Version:           4.0 (using KDE 3.0.3)
Installed from:    SuSE
Compiler:          gcc version 2.95.3 20010315 (SuSE)
OS:          Linux (i686) release 2.4.18-4GB

z-index seems to work for elements that use position: absolute, but if you use position: fixed on an element, that element will always be the top layer in Konqueror - even if the z-index has been set low. In the following example, the #fixed div will be shown as the top layer although it should be at the bottom:

#absolute {
	position: absolute;
	top: 20px;
	left: 20px;
	z-index: 20;
}
#fixed {
	position: fixed;
	top: 20px;
	left: 20px;
	z-index: 10;
}