I have noticed a bug with Expression Web that causes the syntax highlighter to become broken. I was opening the includes/functions.php file out of the phpbb3 forums open source software when I first noticed this. Whats its doing is causing the rest of the file syntax highlighting to look for html and not recognized any further php code. Here is why, it happens when a php closing tag ( ?> ) is done within a php string. For example this will bug the rest of the syntax highlighting to look for html only.
Repro Steps? (N/A for Suggestion)