=head1 NAME

Workarounds for some known bugs in browsers.

=head1 Description

Unfortunately for web programmers, browser bugs are not uncommon, and
sometimes we have to deal with them; refer to this chapter for some
known bugs and how you can work around them.


=head1 Same Browser Requests Serialization

The following feature/bug mostly affects developers.

Certain browsers will serialize requests to the same URL if accessed
from different windows. For example if you have a CGI script that
does:

  for (1..100) {
      print "$$: $_\n";
      warn  "$$: $_\n";
      sleep 1;
  }

And two concurrent requests are issued from different windows of the
same browser (for those browsers that have this bug/feature), the
browser will actually issue only one request and won't run the second
request till the first one is finished. The debug printing to the
error_log file helps to understand the serialization issue.

Solution? Find a UA that doesn't have this feature, especially if a
command line UA will do (LWP comes to mind). As of this writing, opera
6, mozilla 1.0 on linux have this problem, whereas konqueror 3 and
lynx don't.


=head1 Preventing QUERY_STRING from getting corrupted because of &entity key names

In a URL which contains a query string, if the string has multiple
parts separated by ampersands and it contains a key named "reg", for
example C<http://example.com/foo.pl?foo=bar&reg=foobar>, then some
browsers will interpret &reg as an SGML entity and encode it as
C<&reg;>. This will result in a corrupted C<QUERY_STRING>.

The behavior is actually correct, and the problem is that you have
not correctly encoded your ampersands into entities in your HTML. What
you should have in the source of your HTML is
C<http://example.com/foo.pl?foo=bar&amp;reg=foobar>.

A much better, and recommended solution is to separate parameter pairs
with C<;> instead of C<&>. C<CGI.pm>, C<Apache::Request> and
C<$r-E<gt>args()> support a semicolon instead of an ampersand as a
separator. So your URI should look like this:
C<http://example.com/foo.pl?foo=bar;reg=foobar>.  Note that this is
only an issue within HTML documents when you are building your own
URLs with query strings. It is not a problem when the URL is the
result of submitting a form because the browsers have to get that
right. It is also not a problem when typing URLs directly into the
address bar of the browser.

Reference:
http://www.w3.org/TR/1999/REC-html401-19991224/appendix/notes.html#h-B.2.2



=head1 IE 4.x does not re-post data to a non-port-80 URL

One problem with publishing 8080 port numbers (or so I have been 
told) is that IE 4.x has a bug when re-posting data to a non-port-80 
URL.  It drops the port designator and uses port 80 anyway.

See L<Publishing Port Numbers other than
80|guide::config/Publishing_Port_Numbers_other_than_80>.

=head1 Internet Explorer disregards your ErrorDocuments

Many users stumble upon a common problem related to MS Internet
Explorer: if your error response, such as when using C<ErrorDocument
500> or C<$r-E<gt>custom_response>, is too short (which might often be
the case because you aren't very inspired when writing error
messages), Internet Explorer completely disregards it and replaces it
with its own standard error page, even though everything has been sent
correctly by the server and received by the browser.

The solution to this is quite simple: your content needs to be at
least 512 bytes. Microsoft describes some solutions to this I<problem>
here: http://support.microsoft.com/support/kb/articles/Q294/8/07.ASP
. The easiest solution under Perl is to do something like this:

  # write your HTML headers
  print "<!-- ", "_" x 513, " -->";
  # write out the rest of your HTML

Effectively, your content will be long enough, but the user won't
notice any additional content. If you're doing this with static pages,
just insert a long enough comment inside your file to make it large
enough, which will have the same effect.

=head1 Maintainers

Maintainer is the person(s) you should contact with updates,
corrections and patches.

=over

=item *

Stas Bekman [http://stason.org/]

=back


=head1 Authors

=over

=item *

Stas Bekman [http://stason.org/]

=back

Only the major authors are listed above. For contributors see the
Changes file.


=cut