The help item "Language Reference" -> "Expressions" has a problem with the Precedence table. The characters '<' and '>' are not expressed with < and > in the HTML file uppaal2k.jar:com/uppaal/resource/help/System_Descriptions/Expressions.html, causing the help viewer to not display them properly (all < symbols are not shown).
I will update this in the CVS for upcomming releases.
Updated file in CVS with ">" and "<" in precedence table.
I'm reopening the bug, since the 3.4 version has not been updated yet.
I have fixed in for 3.4 as well.