Kompozer can add contradictory 'lang' attributes to line 2. This causes browsers to crash. This bug shows up both in the Xp and *nix version.
An example of such a buggy line is
<html xmlns="http://www.w3.org/1999/xhtml" lang="en" dir="ltr" lang="en-US">
In firefox, this causes an error message of
XML Parsing Error: duplicate attribute
Line Number 2, Column 64:<html xmlns="http://www.w3.org/1999/xhtml" lang="en" dir="ltr" lang="en-US"><head>
Also, Windows Internet Explorer just crashes while trying to open the file.
Editing line two does not work since Kompozer recompiles the line with every save.
Editing the line with notepad to fix the bug by removing one of the 'lang' attributes allows the file to be rendered by browsers... until the next Kompozer save.
A webpage that causes this bug is attached, but I had to leave out the images to get the file to upload. You can see the complete index.xhtml page at