Correcting some HTML boo-boos (not subject to style debates).

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<H1 ALIGN="CENTER">Using XSSI and <SAMP>ErrorDocument</SAMP> to configure

customized international server error responses</H1>

 <LI><A HREF="#listings">HTML listing of the discussed example</A>

</UL>

<HR>

<A NAME="intro"><H2>Introduction</H2></A>

<H2><A NAME="intro">Introduction</A></H2>

This document describes an easy way to provide your apache WWW server

with a set of customized error messages which take advantage of

<A HREF="../content-negotiation.html">Content Negotiation</A>

<P>

An example of a "document not found" message for a german client might

look like this:<BR>

<IMG SRC="../images/custom_errordocs.gif"><BR>

<IMG SRC="../images/custom_errordocs.gif"

 ALT="[Needs graphics capability to display]"><BR>

All links in the document as well as links to the server's administrator

mail address, and even the name and port of the serving virtual host

are inserted in the error document at "run-time", i.e., when the error

actually occurs.

</P>

<A NAME="createdir"><H2>Creating an ErrorDocument directory</H2></A>

<H2><A NAME="createdir">Creating an ErrorDocument directory</A></H2>

For this concept to work as easily as possible, we must take advantage

of as much server support as we can get:

appropriate permissions (readable and executable by the server uid or gid, 

only writable for the administrator).

<A NAME="docnames"><H3>Naming the individual error document files</H3></A>

<H3><A NAME="docnames">Naming the individual error document files</A></H3>

By defining the <SAMP>MultiViews</SAMP> option, the server was told to

automatically scan the directory for matching variants (looking at language

     variant (<A HREF="#fallback">see below</A>).

</UL>

<A NAME="headfoot"><H3>The common header and footer files</H3></A>

<H3><A NAME="headfoot">The common header and footer files</A></H3>

By putting as much layout information in two special "include files", 

the error documents can be reduced to a bare minimum.

implementation of the discussed example.

<A NAME="createdocs"><H3>Creating ErrorDocuments in different languages</H3></A>

<H3><A NAME="createdocs">Creating ErrorDocuments in different languages</A></H3>

After all this preparation work, little remains to be said about the

actual documents. They all share a simple common structure:

of a [400 Bad Request] error document. Documents as simple as that

certainly cause no problems to translate or expand.

<A NAME="fallback"><H3>The fallback language</H3></A>

<H3><A NAME="fallback">The fallback language</A></H3>

Do we need a special handling for languages other than those we have

translations for? We did set the LanguagePriority, didn't we?!

<P>

</P>

<A NAME="listings"><H2>HTML listing of the discussed example</H2></A>

<H2><A NAME="listings">HTML listing of the discussed example</A></H2>

So, to summarize our example, here's the complete listing of the

<SAMP>400.shtml.en</SAMP> document. You will notice that it contains

<A HREF="../mod/mod_browser.html">mod_browser</A>.  Unless otherwise

noted all of these workarounds exist in versions 1.2 and later.

<A name="trailing-crlf"><H3>Trailing CRLF on POSTs</H3></A>

<H3><A name="trailing-crlf">Trailing CRLF on POSTs</A></H3>

<P>This is a legacy issue.  The CERN webserver required <CODE>POST</CODE>

data to have an extra <CODE>CRLF</CODE> following it.  Thus many

Apache works around this problem by eating any empty lines which

appear before a request.

<A name="broken-keepalive"><H3>Broken keepalive</H3></A>

<H3><A name="broken-keepalive">Broken keepalive</A></H3>

<P>Various clients have had broken implementations of <EM>keepalive</EM>

(persistent connections).  In particular the Windows versions of

BrowserMatch "MSIE 4\.0b2;" nokeepalive

</CODE></BLOCKQUOTE>

<A name="force-response-1.0"><H3>Incorrect interpretation of <CODE>HTTP/1.1</CODE> in response</H3></A>

<H3><A name="force-response-1.0">Incorrect interpretation of <CODE>HTTP/1.1</CODE> in response</A></H3>

<P>To quote from section 3.1 of RFC1945:

<BLOCKQUOTE>

HTTP uses a "<MAJOR>.<MINOR>" numbering scheme to indicate versions

HTTP uses a "<MAJOR>.<MINOR>" numbering scheme to indicate versions

of the protocol. The protocol versioning policy is intended to allow

the sender to indicate the format of a message and its capacity for

understanding further HTTP communication, rather than the features

BrowserMatch "RealPlayer 4.0" force-response-1.0

</CODE></BLOCKQUOTE>

<A name="msie4.0b2"><H3>Requests use HTTP/1.1 but responses must be in HTTP/1.0</H3></A>

<H3><A name="msie4.0b2">Requests use HTTP/1.1 but responses must be in HTTP/1.0</A></H3>

<P>MSIE 4.0b2 has this problem.  Its Java VM makes requests in HTTP/1.1

format but the responses must be in HTTP/1.0 format (in particular, it

<A HREF="http://www.apache.org/dist/patches/apply_to_1.2.1/msie_4_0b2_fixes.patch">patch

</A> against 1.2.1.

<A name="257th-byte"><H3>Boundary problems with header parsing</H3></A>

<H3><A name="257th-byte">Boundary problems with header parsing</A></H3>

<P>All versions of Navigator from 2.0 through 4.0b2 (and possibly later)

have a problem if the trailing CRLF of the response header starts at

occur in a response and add extra padding to the header to push the

trailing CRLF past offset 258 of the response.

<A name="boundary-string"><H3>Multipart responses and Quoted Boundary Strings</H3></A>

<H3><A name="boundary-string">Multipart responses and Quoted Boundary Strings</A></H3>

<P>On multipart responses some clients will not accept quotes (")

around the boundary string.  The MIME standard recommends that

Apache does not include quotes on its boundary strings to workaround

this problem.

<A name="byterange-requests"><H3>Byterange requests</H3></A>

<H3><A name="byterange-requests">Byterange requests</A></H3>

<P>A byterange request is used when the client wishes to retrieve a

portion of an object, not necessarily the entire object.  There

version 3.01 is used with it, it will not properly understand byteranges.

The user must upgrade their Acrobat reader to 3.01.

<A name="cookie-merge"><H3><CODE>Set-Cookie</CODE> header is unmergeable</H3></A>

<H3><A name="cookie-merge"><CODE>Set-Cookie</CODE> header is unmergeable</A></H3>

<P>The HTTP specifications say that it is legal to merge headers with

duplicate names into one (separated by semicolon).  Some browsers

headers returned by a CGI, Apache will explicitly avoid merging any

<CODE>Set-Cookie</CODE> headers.

<A name="gif89-expires"><H3><CODE>Expires</CODE> headers and GIF89A animations</H3></A>

<H3><A name="gif89-expires"><CODE>Expires</CODE> headers and GIF89A animations</A></H3>

<P>Navigator versions 2 through 4 will erroneously re-request

GIF89A animations on each loop of the animation if the first

and for <A

HREF="http://www.arctic.org/~dgaudet/patches/apache-1.3-gif89-expires-hack.patch">1.3</A>.

<A name="no-content-length"><H3><CODE>POST</CODE> without <CODE>Content-Length</CODE></H3></A>

<H3><A name="no-content-length"><CODE>POST</CODE> without <CODE>Content-Length</CODE></A></H3>

<P>In certain situations Navigator 3.01 through 3.03 appear to incorrectly

issue a POST without the request body.  There is no

    }

</PRE></BLOCKQUOTE>

<A name="serialize"></A>

The functions <CODE>accept_mutex_on</CODE> and <CODE>accept_mutex_off</CODE>

<A name="serialize">The functions</A>

<CODE>accept_mutex_on</CODE> and <CODE>accept_mutex_off</CODE>

implement a mutual exclusion semaphore.  Only one child can have the

mutex at any time.  There are several choices for implementing these

mutexes.  The choice is defined in <CODE>src/conf.h</CODE> (pre-1.3) or

<HR>

<A name="serverroot">

<H2>Permissions on ServerRoot Directories</H2></A>

<H2><A name="serverroot">Permissions on ServerRoot Directories</A></H2>

<P>In typical operation, Apache is started by the root

user, and it switches to the user defined by the <A

HREF="../mod/core.html#user"><STRONG>User</STRONG></A> directive to serve hits.

<CENTER>

<A name="Configuration">

<H1>Configuration Directives</H1>

</A>

<H1><A NAME="Configuration">Configuration Directives</A></H1>

</CENTER>

<A name="RewriteEngine"><H3>RewriteEngine</H3></A>

<H3><A NAME="RewriteEngine">RewriteEngine</A></H3>

<A

 HREF="directive-dict.html#Syntax"

 REL="Help"

<hr noshade size=1>

<P>

<A name="RewriteOptions"><H3>RewriteOptions</H3></A>

<H3><A NAME="RewriteOptions">RewriteOptions</A></H3>

<A

 HREF="directive-dict.html#Syntax"

 REL="Help"

<hr noshade size=1>

<P>

<A name="RewriteLog"><H3>RewriteLog</H3></A>

<H3><A NAME="RewriteLog">RewriteLog</A></H3>

<A

 HREF="directive-dict.html#Syntax"

 REL="Help"

<hr noshade size=1>

<P>

<A name="RewriteLogLevel"><H3>RewriteLogLevel</H3></A>

<H3><A NAME="RewriteLogLevel">RewriteLogLevel</A></H3>

<A

 HREF="directive-dict.html#Syntax"

 REL="Help"

<hr noshade size=1>

<P>

<A name="RewriteMap"><H3>RewriteMap</H3></A>

<H3><A NAME="RewriteMap">RewriteMap</A></H3>

<A

 HREF="directive-dict.html#Syntax"

 REL="Help"

to insert/substitute fields through a key lookup.

<P>

The <A name="mapfunc"><EM>Mapname</EM></A> is the name of the map and will

The <A NAME="mapfunc"><EM>Mapname</EM></A> is the name of the map and will

be used to specify a mapping-function for the substitution strings of a

rewriting rule via

<hr noshade size=1>

<P>

<A name="RewriteBase"><H3>RewriteBase</H3></A>

<H3><A NAME="RewriteBase">RewriteBase</A></H3>

<A

 HREF="directive-dict.html#Syntax"

 REL="Help"

<hr noshade size=1>

<P>

<A name="RewriteCond"><H3>RewriteCond</H3></A>

<H3><A NAME="RewriteCond">RewriteCond</A></H3>

<A

 HREF="directive-dict.html#Syntax"

 REL="Help"

<TT>$N</TT>

</STRONG></BLOCKQUOTE>

(1 <= N <= 9) which provide access to the grouped parts (parenthesis!) of the

(1 <= N <= 9) which provide access to the grouped parts (parenthesis!)

of the

pattern from the corresponding <TT>RewriteRule</TT> directive (the one

following the current bunch of <TT>RewriteCond</TT> directives).

<TT>%N</TT>

</STRONG></BLOCKQUOTE>

(1 <= N <= 9) which provide access to the grouped parts (parenthesis!) of the

(1 <= N <= 9) which provide access to the grouped parts (parenthesis!) of the

pattern from the last matched <TT>RewriteCond</TT> directive in the current

bunch of conditions.

<hr noshade size=1>

<P>

<A name="RewriteRule"><H3>RewriteRule</H3></A>

<H3><A NAME="RewriteRule">RewriteRule</A></H3>

<A

 HREF="directive-dict.html#Syntax"

 REL="Help"

run-time.

<P>

<A name="patterns"><EM>Pattern</EM></A> can be (for Apache 1.1.x a System

V8 and for Apache 1.2.x a POSIX) <A name="regexp">regular expression</A>

<A NAME="patterns"><EM>Pattern</EM></A> can be (for Apache 1.1.x a System

V8 and for Apache 1.2.x a POSIX) <A NAME="regexp">regular expression</A>

which gets applied to the current URL. Here ``current'' means the value of the

URL when this rule gets applied. This may not be the original requested

URL, because there could be any number of rules before which already matched

</TABLE>

<P>

<A name="rhs"><EM>Substitution</EM></A> of a rewriting rule is the string

<A NAME="rhs"><EM>Substitution</EM></A> of a rewriting rule is the string

which is substituted for (or replaces) the original URL for which

<EM>Pattern</EM> matched.  Beside plain text you can use

comma-separated list of the following flags:

<UL>

<LI>'<STRONG><CODE>redirect|R</CODE>[=<EM>code</EM>]</STRONG>' (force <A name="redirect"><STRONG>r</STRONG>edirect</A>)<BR>

<LI>'<STRONG><CODE>redirect|R</CODE>[=<EM>code</EM>]</STRONG>' (force <A NAME="redirect"><STRONG>r</STRONG>edirect</A>)<BR>

    Prefix <EM>Substitution</EM>

    with <CODE>http://thishost[:thisport]/</CODE> (which makes the new URL a URI) to

    force a external redirection. If no <EM>code</EM> is given a HTTP response

<!--/%hypertext -->

<CENTER>

<A name="Additional">

<H1>Additional Features</H1>

</A>

<H1><A NAME="Additional">Additional Features</A></H1>

</CENTER>

<A name="EnvVar">

<H2>Environment Variables</H2>

</A>

<H2><A NAME="EnvVar">Environment Variables</A></H2>

This module keeps track of two additional (non-standard) CGI/SSI environment

variables named <TT>SCRIPT_URL</TT> and <TT>SCRIPT_URI</TT>. These contain