Selection of comment text in IE broken. (Fix Inside)

Trying to select text within comments to a forum thread does not work under IE. To replicate this bug view any forum thread (such as http://drupal.org/node/44934) and try to highlight text within user comments using IE. You won't be able to or you'll only be able to select the entire block.

This is a bug in IE, not Drupal or the forum system. However there is a workaround that needs to be applied at the base system.

The root cause here is how IE handles the BASE tag. This bug pops up only when viewing a page that puts IE into standards mode. A quirks-mode page will not have this bug. The fix is to insert a closing BASE tag into the HTML. But a closing base tag is invalid HTML 4 (it's valid XHTML). So to work around that we can use IE conditional comments. It keeps the markup HTML 4 and XHTML valid and resolves this issue.

The new BASE tag generated by Drupal should look something like this:

<base href="http://drupal.org/"><!--[if IE]></base><![endif]-->

This fix does not put IE into quirks mode. This fix has no impact on other browsers.