Version:           4.0 (using KDE 3.1.9)
Compiler:          gcc version 3.2.2 (Mandrake Linux 9.1 3.2.2-3mdk)
OS:          Linux (i686) release 2.4.21-0.13mdk

I don't know if the bug occur with the stable version of Konqueror (3.1.1) but it occurs with the CVS version.

When khtml don't understand the rules of a CSS, for example display : compact or display:run-in, it seems that it replace it with display:none.
That's a bad idea because we lose some information.

Here are examples : 
http://www.editions-eyrolles.com/css2/tests/vfm/vfm4.htm et http://www.editions-eyrolles.com/css2/tests/vfm/vfm5.htm

Other related bugs are 
http://bugs.kde.org/show_bug.cgi?id=33592 and http://bugs.kde.org/show_bug.cgi?id=33591 but they don't insist on the real problem : If the CSS parser don't understand a new rule, ignore it but don't replace it by a wrong one (display:none for example)

"A user agent must ignore a declaration with an invalid property name or an invalid value." cf http://www.w3.org/TR/REC-CSS2/syndata.html#declaration