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39 >Privoxy 3.0.7 User Manual</TH
81 >14.1. Regular Expressions</H2
86 > uses Perl-style <SPAN
91 HREF="actions-file.html"
95 HREF="filter-file.html"
99 HREF="http://www.pcre.org/"
108 > If you are reading this, you probably don't understand what <SPAN
112 > are, or what they can do. So this will be a very brief
113 introduction only. A full explanation would require a <A
114 HREF="http://www.oreilly.com/catalog/regex/"
119 > Regular expressions provide a language to describe patterns that can be
120 run against strings of characters (letter, numbers, etc), to see if they
121 match the string or not. The patterns are themselves (sometimes complex)
122 strings of literal characters, combined with wild-cards, and other special
123 characters, called meta-characters. The <SPAN
125 >"meta-characters"</SPAN
127 special meanings and are used to build complex patterns to be matched against.
128 Perl Compatible Regular Expressions are an especially convenient
132 > of the regular expression language.</P
134 > To make a simple analogy, we do something similar when we use wild-card
135 characters when listing files with the <B
142 > matches all filenames. The <SPAN
146 character here is the asterisk which matches any and all characters. We can be
147 more specific and use <TT
150 > to match just individual
153 >"dir file?.text"</SPAN
161 >, etc. We are pattern
162 matching, using a similar technique to <SPAN
164 >"regular expressions"</SPAN
167 > Regular expressions do essentially the same thing, but are much, much more
168 powerful. There are many more <SPAN
170 >"special characters"</SPAN
172 building complex patterns however. Let's look at a few of the common ones,
173 and then some examples:</P
188 > - Matches any single character, e.g. <SPAN
226 > - The preceding character or expression is matched ZERO or ONE
249 > - The preceding character or expression is matched ONE or MORE
272 > - The preceding character or expression is matched ZERO or MORE
298 > character denotes that
299 the following character should be taken literally. This is used where one of the
300 special characters (e.g. <SPAN
303 >) needs to be taken literally and
304 not as a special meta-character. Example: <SPAN
306 >"example\.com"</SPAN
308 sure the period is recognized only as a period (and not expanded to its
309 meta-character meaning of any single character).
331 > - Characters enclosed in brackets will be matched if
332 any of the enclosed characters are encountered. For instance, <SPAN
336 matches any numeric digit (zero through nine). As an example, we can combine
340 > to match any digit one of more times: <SPAN
365 > - parentheses are used to group a sub-expression,
366 or multiple sub-expressions.
391 > character works like an
395 > conditional statement. A match is successful if the
396 sub-expression on either side of <SPAN
399 > matches. As an example:
402 >"/(this|that) example/"</SPAN
403 > uses grouping and the bar character
404 and would match either <SPAN
406 >"this example"</SPAN
420 > These are just some of the ones you are likely to use when matching URLs with
424 >, and is a long way from a definitive
425 list. This is enough to get us started with a few simple examples which may
426 be more illuminating:</P
438 that uses the common combination of <SPAN
445 denote any character, zero or more times. In other words, any string at all.
446 So we start with a literal forward slash, then our regular expression pattern
450 >) another literal forward slash, the string
454 >, another forward slash, and lastly another
459 a directory path here. This will match any file with the path that has a
460 directory named <SPAN
467 any characters, and this could conceivably be more forward slashes, so it
468 might expand into a much longer looking path. For example, this could match:
471 >"/eye/hate/spammers/banners/annoy_me_please.gif"</SPAN
475 >"/banners/annoying.html"</SPAN
476 >, or almost an infinite number of other
477 possible combinations, just so it has <SPAN
483 > And now something a little more complex:</P
491 >/.*/adv((er)?ts?|ertis(ing|ements?))?/</TT
495 We have several literal forward slashes again (<SPAN
499 building another expression that is a file path statement. We have another
503 >, so we are matching against any conceivable sub-path, just so
504 it matches our expression. The only true literal that <SPAN
511 > our pattern is <SPAN
515 the forward slashes. What comes after the <SPAN
519 interesting part. </P
524 > means the preceding expression (either a
525 literal character or anything grouped with <SPAN
529 can exist or not, since this means either zero or one match. So
532 >"((er)?ts?|ertis(ing|ements?))"</SPAN
533 > is optional, as are the
534 individual sub-expressions: <SPAN
540 >"(ing|ements?)"</SPAN
551 >. We have two of those. For instance,
554 >"(ing|ements?)"</SPAN
555 >, can expand to match either <SPAN
568 >. What is being done here, is an
569 attempt at matching as many variations of <SPAN
571 >"advertisement"</SPAN
573 similar, as possible. So this would expand to match just <SPAN
589 >"advertisement"</SPAN
593 >"advertisements"</SPAN
594 >. You get the idea. But it would not match
597 >"advertizements"</SPAN
601 >). We could fix that by
602 changing our regular expression to:
605 >"/.*/adv((er)?ts?|erti(s|z)(ing|ements?))?/"</SPAN
606 >, which would then match
615 >/.*/advert[0-9]+\.(gif|jpe?g)</TT
619 another path statement with forward slashes. Anything in the square brackets
623 > can be matched. This is using <SPAN
627 shorthand expression to mean any digit one through nine. It is the same as
631 >. So any digit matches. The <SPAN
635 means one or more of the preceding expression must be included. The preceding
636 expression here is what is in the square brackets -- in this case, any digit
637 one through nine. Then, at the end, we have a grouping: <SPAN
641 This includes a <SPAN
644 >, so this needs to match the expression on
645 either side of that bar character also. A simple <SPAN
648 > on one side, and the other
649 side will in turn match either <SPAN
659 > means the letter <SPAN
663 can be matched once or not at all. So we are building an expression here to
664 match image GIF or JPEG type image file. It must include the literal
668 >, then one or more digits, and a <SPAN
672 (which is now a literal, and not a special character, since it is escaped
676 >), and lastly either <SPAN
686 >. Some possible matches would
689 >"//advert1.jpg"</SPAN
693 >"/nasty/ads/advert1234.gif"</SPAN
697 >"/banners/from/hell/advert99.jpg"</SPAN
698 >. It would not match
702 > (no leading slash), or
705 >"/adverts232.jpg"</SPAN
706 > (the expression does not include an
712 >"/advert1.jsp"</SPAN
717 in the expression anywhere).</P
719 > We are barely scratching the surface of regular expressions here so that you
720 can understand the default <SPAN
724 configuration files, and maybe use this knowledge to customize your own
725 installation. There is much, much more that can be done with regular
726 expressions. Now that you know enough to get started, you can learn more on
729 > More reading on Perl Compatible Regular expressions:
731 HREF="http://perldoc.perl.org/perlre.html"
733 >http://perldoc.perl.org/perlre.html</A
736 > For information on regular expression based substitutions and their applications
737 in filters, please see the <A
738 HREF="filter-file.html"
739 >filter file tutorial</A
750 >14.2. Privoxy's Internal Pages</H2
755 > proxies each requested
756 web page, it is easy for <SPAN
760 trap certain special URLs. In this way, we can talk directly to
765 configured, see how our rules are being applied, change these
766 rules and other configuration options, and even turn
770 > filtering off, all with
771 a web browser. </P
773 > The URLs listed below are the special ones that allow direct access
781 > must be running to access these. If
782 not, you will get a friendly error message. Internet access is not
801 HREF="http://config.privoxy.org/"
803 >http://config.privoxy.org/</A
808 > There is a shortcut: <A
813 doesn't provide a fall-back to a real page, in case the request is not
823 Show information about the current configuration, including viewing and
824 editing of actions files:
834 HREF="http://config.privoxy.org/show-status"
836 >http://config.privoxy.org/show-status</A
844 Show the source code version numbers:
854 HREF="http://config.privoxy.org/show-version"
856 >http://config.privoxy.org/show-version</A
864 Show the browser's request headers:
874 HREF="http://config.privoxy.org/show-request"
876 >http://config.privoxy.org/show-request</A
884 Show which actions apply to a URL and why:
894 HREF="http://config.privoxy.org/show-url-info"
896 >http://config.privoxy.org/show-url-info</A
904 Toggle Privoxy on or off. In this case, <SPAN
908 to run, but only as a pass-through proxy, with no actions taking place:
918 HREF="http://config.privoxy.org/toggle"
920 >http://config.privoxy.org/toggle</A
925 > Short cuts. Turn off, then on:
935 HREF="http://config.privoxy.org/toggle?set=disable"
937 >http://config.privoxy.org/toggle?set=disable</A
949 HREF="http://config.privoxy.org/toggle?set=enable"
951 >http://config.privoxy.org/toggle?set=enable</A
959 > These may be bookmarked for quick reference. See next. </P
967 >14.2.1. Bookmarklets</H3
969 > Below are some <SPAN
971 >"bookmarklets"</SPAN
972 > to allow you to easily access a
976 > version of some of <SPAN
980 special pages. They are designed for MS Internet Explorer, but should work
981 equally well in Netscape, Mozilla, and other browsers which support
982 JavaScript. They are designed to run directly from your bookmarks - not by
983 clicking the links below (although that should work for testing).</P
985 > To save them, right-click the link and choose <SPAN
987 >"Add to Favorites"</SPAN
991 >"Add Bookmark"</SPAN
992 > (Netscape). You will get a warning that
995 >"may not be safe"</SPAN
996 > - just click OK. Then you can run the
997 Bookmarklet directly from your favorites/bookmarks. For even faster access,
998 you can put them on the <SPAN
1001 > bar (IE) or the <SPAN
1005 > (Netscape), and run them with a single click. </P
1013 HREF="javascript:void(window.open('http://config.privoxy.org/toggle?mini=y&set=enabled','ijbstatus','width=250,height=100,resizable=yes,scrollbars=no,toolbar=no,location=no,directories=no,status=no,menubar=no,copyhistory=no').focus());"
1015 >Privoxy - Enable</A
1022 HREF="javascript:void(window.open('http://config.privoxy.org/toggle?mini=y&set=disabled','ijbstatus','width=250,height=100,resizable=yes,scrollbars=no,toolbar=no,location=no,directories=no,status=no,menubar=no,copyhistory=no').focus());"
1024 >Privoxy - Disable</A
1031 HREF="javascript:void(window.open('http://config.privoxy.org/toggle?mini=y&set=toggle','ijbstatus','width=250,height=100,resizable=yes,scrollbars=no,toolbar=no,location=no,directories=no,status=no,menubar=no,copyhistory=no').focus());"
1033 >Privoxy - Toggle Privoxy</A
1034 > (Toggles between enabled and disabled)
1040 HREF="javascript:void(window.open('http://config.privoxy.org/toggle?mini=y','ijbstatus','width=250,height=2,resizable=yes,scrollbars=no,toolbar=no,location=no,directories=no,status=no,menubar=no,copyhistory=no').focus());"
1042 >Privoxy- View Status</A
1049 HREF="javascript:void(window.open('http://config.privoxy.org/show-url-info?url='+escape(location.href),'Why').focus());"
1058 > Credit: The site which gave us the general idea for these bookmarklets is
1060 HREF="http://www.bookmarklets.com/"
1062 >www.bookmarklets.com</A
1064 have more information about bookmarklets. </P
1074 >14.3. Chain of Events</H2
1076 > Let's take a quick look at how some of <SPAN
1080 core features are triggered, and the ensuing sequence of events when a web
1081 page is requested by your browser:</P
1088 > First, your web browser requests a web page. The browser knows to send
1089 the request to <SPAN
1092 >, which will in turn,
1093 relay the request to the remote web server after passing the following
1102 > traps any request for its own internal CGI
1107 >) and sends the CGI page back to the browser.
1115 > checks to see if the URL
1117 HREF="actions-file.html#BLOCK"
1123 so, the URL is then blocked, and the remote web server will not be contacted.
1125 HREF="actions-file.html#HANDLE-AS-IMAGE"
1128 >"+handle-as-image"</SPAN
1133 HREF="actions-file.html#HANDLE-AS-EMPTY-DOCUMENT"
1136 >"+handle-as-empty-document"</SPAN
1139 are then checked, and if there is no match, an
1143 > page is sent back to the browser. Otherwise, if
1144 it does match, an image is returned for the former, and an empty text
1145 document for the latter. The type of image would depend on the setting of
1147 HREF="actions-file.html#SET-IMAGE-BLOCKER"
1150 >"+set-image-blocker"</SPAN
1153 (blank, checkerboard pattern, or an HTTP redirect to an image elsewhere).
1158 > Untrusted URLs are blocked. If URLs are being added to the
1162 > file, then that is done.
1167 > If the URL pattern matches the <A
1168 HREF="actions-file.html#FAST-REDIRECTS"
1171 >"+fast-redirects"</SPAN
1174 it is then processed. Unwanted parts of the requested URL are stripped.
1179 > Now the rest of the client browser's request headers are processed. If any
1180 of these match any of the relevant actions (e.g. <A
1181 HREF="actions-file.html#HIDE-USER-AGENT"
1184 >"+hide-user-agent"</SPAN
1187 etc.), headers are suppressed or forged as determined by these actions and
1193 > Now the web server starts sending its response back (i.e. typically a web
1199 > First, the server headers are read and processed to determine, among other
1200 things, the MIME type (document type) and encoding. The headers are then
1201 filtered as determined by the
1203 HREF="actions-file.html#CRUNCH-INCOMING-COOKIES"
1206 >"+crunch-incoming-cookies"</SPAN
1210 HREF="actions-file.html#SESSION-COOKIES-ONLY"
1213 >"+session-cookies-only"</SPAN
1217 HREF="actions-file.html#DOWNGRADE-HTTP-VERSION"
1220 >"+downgrade-http-version"</SPAN
1229 HREF="actions-file.html#KILL-POPUPS"
1232 >"+kill-popups"</SPAN
1235 action applies, and it is an HTML or JavaScript document, the popup-code in the
1236 response is filtered on-the-fly as it is received.
1242 HREF="actions-file.html#FILTER"
1249 HREF="actions-file.html#DEANIMATE-GIFS"
1252 >"+deanimate-gifs"</SPAN
1255 action applies (and the document type fits the action), the rest of the page is
1256 read into memory (up to a configurable limit). Then the filter rules (from
1260 > and any other filter files) are
1261 processed against the buffered content. Filters are applied in the order
1262 they are specified in one of the filter files. Animated GIFs, if present,
1263 are reduced to either the first or last frame, depending on the action
1264 setting.The entire page, which is now filtered, is then sent by
1268 > back to your browser.
1272 HREF="actions-file.html#FILTER"
1279 HREF="actions-file.html#DEANIMATE-GIFS"
1282 >"+deanimate-gifs"</SPAN
1288 > passes the raw data through
1289 to the client browser as it becomes available.
1294 > As the browser receives the now (possibly filtered) page content, it
1295 reads and then requests any URLs that may be embedded within the page
1296 source, e.g. ad images, stylesheets, JavaScript, other HTML documents (e.g.
1297 frames), sounds, etc. For each of these objects, the browser issues a
1298 separate request (this is easily viewable in <SPAN
1302 logs). And each such request is in turn processed just as above. Note that a
1303 complex web page will have many, many such embedded URLs. If these
1304 secondary requests are to a different server, then quite possibly a very
1305 differing set of actions is triggered.
1311 > NOTE: This is somewhat of a simplistic overview of what happens with each URL
1312 request. For the sake of brevity and simplicity, we have focused on
1316 > core features only.</P
1325 >14.4. Troubleshooting: Anatomy of an Action</H2
1332 HREF="actions-file.html#ACTIONS"
1335 HREF="actions-file.html#FILTER"
1338 to any given URL can be complex, and not always so
1339 easy to understand what is happening. And sometimes we need to be able to
1350 doing. Especially, if something <SPAN
1354 is causing us a problem inadvertently. It can be a little daunting to look at
1355 the actions and filters files themselves, since they tend to be filled with
1357 HREF="appendix.html#REGEX"
1358 >regular expressions</A
1359 > whose consequences are not
1360 always so obvious. </P
1362 > One quick test to see if <SPAN
1365 > is causing a problem
1366 or not, is to disable it temporarily. This should be the first troubleshooting
1368 HREF="appendix.html#BOOKMARKLETS"
1369 >the Bookmarklets</A
1370 > section on a quick
1371 and easy way to do this (be sure to flush caches afterward!). Looking at the
1372 logs is a good idea too.</P
1374 > Another easy troubleshooting step to try is if you have done any
1375 customization of your installation, revert back to the installed
1376 defaults and see if that helps. There are times the developers get complaints
1377 about one thing or another, and the problem is more related to a customized
1378 configuration issue.</P
1385 HREF="http://config.privoxy.org/show-url-info"
1387 >http://config.privoxy.org/show-url-info</A
1389 page that can show us very specifically how <SPAN
1393 are being applied to any given URL. This is a big help for troubleshooting.</P
1395 > First, enter one URL (or partial URL) at the prompt, and then
1400 how the current configuration will handle it. This will not
1401 help with filtering effects (i.e. the <A
1402 HREF="actions-file.html#FILTER"
1408 one of the filter files since this is handled very
1409 differently and not so easy to trap! It also will not tell you about any other
1410 URLs that may be embedded within the URL you are testing. For instance, images
1411 such as ads are expressed as URLs within the raw page source of HTML pages. So
1412 you will only get info for the actual URL that is pasted into the prompt area
1413 -- not any sub-URLs. If you want to know about embedded URLs like ads, you
1414 will have to dig those out of the HTML source. Use your browser's <SPAN
1418 > option for this. Or right click on the ad, and grab the
1421 > Let's try an example, <A
1422 HREF="http://google.com"
1426 and look at it one section at a time in a sample configuration (your real
1427 configuration may vary):</P
1437 > Matches for http://google.com:
1439 In file: default.action <SPAN
1449 -client-header-filter{hide-tor-exit-notation}
1450 -content-type-overwrite
1451 -crunch-client-header
1452 -crunch-if-none-match
1453 -crunch-incoming-cookies
1454 -crunch-outgoing-cookies
1455 -crunch-server-header
1456 +deanimate-gifs {last}
1457 -downgrade-http-version
1458 +fast-redirects {check-decoded-url}
1460 -filter {content-cookies}
1461 -filter {all-popups}
1462 -filter {banners-by-link}
1463 -filter {tiny-textforms}
1464 -filter {frameset-borders}
1465 -filter {demoronizer}
1466 -filter {shockwave-flash}
1467 -filter {quicktime-kioskmode}
1469 -filter {crude-parental}
1470 -filter {site-specifics}
1471 -filter {js-annoyances}
1472 -filter {html-annoyances}
1473 +filter {refresh-tags}
1474 -filter {unsolicited-popups}
1475 +filter {img-reorder}
1476 +filter {banners-by-size}
1478 +filter {jumping-windows}
1479 +filter {ie-exploits}
1486 -handle-as-empty-document
1488 -hide-accept-language
1489 -hide-content-disposition
1490 +hide-forwarded-for-headers
1491 +hide-from-header {block}
1492 -hide-if-modified-since
1493 +hide-referrer {forge}
1498 -overwrite-last-modified
1499 +prevent-compression
1503 -server-header-filter{xml-to-html}
1504 -server-header-filter{html-to-xml}
1505 +session-cookies-only
1506 +set-image-blocker {pattern}
1507 -treat-forbidden-connects-like-blocks }
1510 { -session-cookies-only }
1516 In file: user.action <SPAN
1523 (no matches in this file) </PRE
1529 > This is telling us how we have defined our
1531 HREF="actions-file.html#ACTIONS"
1537 which ones match for our test case, <SPAN
1541 Displayed is all the actions that are available to us. Remember,
1545 > sign denotes <SPAN
1555 >. So some are <SPAN
1562 >. Each example we try may provide a slightly different
1563 end result, depending on our configuration directives.</P
1569 > file. The large, multi-line
1570 listing, is how the actions are set to match for all URLs, i.e. our default
1571 settings. If you look at your <SPAN
1574 > file, this would be the
1575 section just below the <SPAN
1578 > section near the top. This
1579 will apply to all URLs as signified by the single forward slash at the end
1580 of the listing -- <SPAN
1585 > But we have defined additional actions that would be exceptions to these general
1586 rules, and then we list specific URLs (or patterns) that these exceptions
1587 would apply to. Last match wins. Just below this then are two explicit
1590 >".google.com"</SPAN
1591 >. The first is negating our previous
1592 cookie setting, which was for <A
1593 HREF="actions-file.html#SESSION-COOKIES-ONLY"
1596 >"+session-cookies-only"</SPAN
1599 (i.e. not persistent). So we will allow persistent cookies for google, at
1600 least that is how it is in this example. The second turns
1608 HREF="actions-file.html#FAST-REDIRECTS"
1611 >"+fast-redirects"</SPAN
1614 action, allowing this to take place unmolested. Note that there is a leading
1617 >".google.com"</SPAN
1618 >. This will match any hosts and
1619 sub-domains, in the google.com domain also, such as
1622 >"www.google.com"</SPAN
1625 >"mail.google.com"</SPAN
1629 >"www.google.de"</SPAN
1630 >! So, apparently, we have these two actions
1631 defined as exceptions to the general rules at the top somewhere in the lower
1639 > is referenced somewhere in these latter sections.</P
1644 > file, we again have no hits.
1645 So there is nothing google-specific that we might have added to our own, local
1646 configuration. If there was, those actions would over-rule any actions from
1647 previously processed files, such as <TT
1654 > typically has the last word. This is the
1655 best place to put hard and fast exceptions,</P
1657 > And finally we pull it all together in the bottom section and summarize how
1661 > is applying all its <SPAN
1678 > Final results:
1682 -client-header-filter{hide-tor-exit-notation}
1683 -content-type-overwrite
1684 -crunch-client-header
1685 -crunch-if-none-match
1686 -crunch-incoming-cookies
1687 -crunch-outgoing-cookies
1688 -crunch-server-header
1689 +deanimate-gifs {last}
1690 -downgrade-http-version
1691 +fast-redirects {check-decoded-url}
1693 -filter {content-cookies}
1694 -filter {all-popups}
1695 -filter {banners-by-link}
1696 -filter {tiny-textforms}
1697 -filter {frameset-borders}
1698 -filter {demoronizer}
1699 -filter {shockwave-flash}
1700 -filter {quicktime-kioskmode}
1702 -filter {crude-parental}
1703 -filter {site-specifics}
1704 -filter {js-annoyances}
1705 -filter {html-annoyances}
1706 +filter {refresh-tags}
1707 -filter {unsolicited-popups}
1708 +filter {img-reorder}
1709 +filter {banners-by-size}
1711 +filter {jumping-windows}
1712 +filter {ie-exploits}
1719 -handle-as-empty-document
1721 -hide-accept-language
1722 -hide-content-disposition
1723 +hide-forwarded-for-headers
1724 +hide-from-header {block}
1725 -hide-if-modified-since
1726 +hide-referrer {forge}
1731 -overwrite-last-modified
1732 +prevent-compression
1736 -server-header-filter{xml-to-html}
1737 -server-header-filter{html-to-xml}
1738 -session-cookies-only
1739 +set-image-blocker {pattern}
1740 -treat-forbidden-connects-like-blocks </PRE
1746 > Notice the only difference here to the previous listing, is to
1749 >"fast-redirects"</SPAN
1752 >"session-cookies-only"</SPAN
1754 which are activated specifically for this site in our configuration,
1755 and thus show in the <SPAN
1757 >"Final Results"</SPAN
1760 > Now another example, <SPAN
1762 >"ad.doubleclick.net"</SPAN
1779 { +block +handle-as-image }
1780 .[a-vx-z]*.doubleclick.net</PRE
1786 > We'll just show the interesting part here - the explicit matches. It is
1787 matched three different times. Two <SPAN
1793 >"+block +handle-as-image"</SPAN
1795 which is the expanded form of one of our aliases that had been defined as:
1798 >"+block-as-image"</SPAN
1800 HREF="actions-file.html#ALIASES"
1806 the first section of the actions file and typically used to combine more
1807 than one action.)</P
1809 > Any one of these would have done the trick and blocked this as an unwanted
1810 image. This is unnecessarily redundant since the last case effectively
1811 would also cover the first. No point in taking chances with these guys
1812 though ;-) Note that if you want an ad or obnoxious
1813 URL to be invisible, it should be defined as <SPAN
1815 >"ad.doubleclick.net"</SPAN
1817 is done here -- as both a <A
1818 HREF="actions-file.html#BLOCK"
1832 HREF="actions-file.html#HANDLE-AS-IMAGE"
1835 >"+handle-as-image"</SPAN
1838 The custom alias <SPAN
1842 >+block-as-image</TT
1845 simplifies the process and make it more readable.</P
1847 > One last example. Let's try <SPAN
1849 >"http://www.example.net/adsl/HOWTO/"</SPAN
1851 This one is giving us problems. We are getting a blank page. Hmmm ...</P
1861 > Matches for http://www.example.net/adsl/HOWTO/:
1863 In file: default.action <SPAN
1873 -client-header-filter{hide-tor-exit-notation}
1874 -content-type-overwrite
1875 -crunch-client-header
1876 -crunch-if-none-match
1877 -crunch-incoming-cookies
1878 -crunch-outgoing-cookies
1879 -crunch-server-header
1881 -downgrade-http-version
1882 +fast-redirects {check-decoded-url}
1884 -filter {content-cookies}
1885 -filter {all-popups}
1886 -filter {banners-by-link}
1887 -filter {tiny-textforms}
1888 -filter {frameset-borders}
1889 -filter {demoronizer}
1890 -filter {shockwave-flash}
1891 -filter {quicktime-kioskmode}
1893 -filter {crude-parental}
1894 -filter {site-specifics}
1895 -filter {js-annoyances}
1896 -filter {html-annoyances}
1897 +filter {refresh-tags}
1898 -filter {unsolicited-popups}
1899 +filter {img-reorder}
1900 +filter {banners-by-size}
1902 +filter {jumping-windows}
1903 +filter {ie-exploits}
1910 -handle-as-empty-document
1912 -hide-accept-language
1913 -hide-content-disposition
1914 +hide-forwarded-for-headers
1915 +hide-from-header{block}
1916 +hide-referer{forge}
1920 -overwrite-last-modified
1921 +prevent-compression
1925 -server-header-filter{xml-to-html}
1926 -server-header-filter{html-to-xml}
1927 +session-cookies-only
1928 +set-image-blocker{blank}
1929 -treat-forbidden-connects-like-blocks }
1932 { +block +handle-as-image }
1946 configuration! But we did not want this at all! Now we see why we get the
1947 blank page. It is actually triggering two different actions here, and
1948 the effects are aggregated so that the URL is blocked, and <SPAN
1952 to treat the block as if it were an image. But this is, of course, all wrong.
1953 We could now add a new action below this (or better in our own
1957 > file) that explicitly
1966 HREF="actions-file.html#BLOCK"
1975 > in them (remember, last match in the configuration
1976 wins). There are various ways to handle such exceptions. Example:</P
1993 > Now the page displays ;-)
1994 Remember to flush your browser's caches when making these kinds of changes to
1995 your configuration to insure that you get a freshly delivered page! Or, try
2001 > But now what about a situation where we get no explicit matches like
2012 > { +block +handle-as-image }
2019 > That actually was very helpful and pointed us quickly to where the problem
2020 was. If you don't get this kind of match, then it means one of the default
2021 rules in the first section of <TT
2025 the problem. This would require some guesswork, and maybe a little trial and
2026 error to isolate the offending rule. One likely cause would be one of the
2028 HREF="actions-file.html#FILTER"
2034 These tend to be harder to troubleshoot.
2035 Try adding the URL for the site to one of aliases that turn off
2037 HREF="actions-file.html#FILTER"
2054 .worldpay.com # for quietpc.com
2077 >{ -filter -session-cookies-only }</TT
2080 Or you could do your own exception to negate filtering: </P
2091 # Disable ALL filter actions for sites in this section
2100 > This would turn off all filtering for these sites. This is best
2105 exceptions. Note that when a simple domain pattern is used by itself (without
2106 the subsequent path portion), all sub-pages within that domain are included
2107 automatically in the scope of the action.</P
2109 > Images that are inexplicably being blocked, may well be hitting the
2111 HREF="actions-file.html#FILTER-BANNERS-BY-SIZE"
2114 >"+filter{banners-by-size}"</SPAN
2118 that images of certain sizes are ad banners (works well
2123 >most of the time</I
2125 > since these tend to be standardized).</P
2133 > is an alias that disables most
2134 actions that are the most likely to cause trouble. This can be used as a
2135 last resort for problem sites. </P
2146 # Handle with care: easy to break
2148 mybank.example.com</PRE
2158 >Remember to flush caches!</I
2164 > reference lacks the TLD portion (e.g.
2168 >. This will effectively match any TLD with
2172 > in it, such as <TT
2176 just as an example.</P
2179 If this still does not work, you will have to go through the remaining
2180 actions one by one to find which one(s) is causing the problem.</P
2188 SUMMARY="Footer navigation table"