Version: (using KDE KDE 3.5.5) Installed from: Debian stable Packages Reported in Debian BTS at http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=357019 Package: konqueror Version: 4:3.3.2-1sarge1 Test Case: <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en"> <head> <title> Faulty Centering </title> <style> body { color: white; background: black; padding: 0; } div { position: absolute; top: 0px; right: 0px; bottom: 0px; left: 0px; color: black; background: white; margin: auto; width: 640px; height: 400px; } </style> </head> <body> <div> Fully centered white box with important information... </div> </body> </html> If the browser window is large enought, one gets a fully centered white box with text on black background. If one resizes the window until the box does not fit anymore (reload necessary), parts of the box get inaccessible and the text gets lost. The left/top margin must not get negative so that the white box stays left and/or top aligned (cf. CSS 2.1, 10.3.7 and 10.6.4: If none of the three is 'auto'...). Firefox does this correctly.
running Konqueror 3.5.7 on a Gentoo box, I can confirm the described behaviour. btw, in contrast to Firefox, Opera 9.21 does the same.
it is correct that left/right margins must not become negative in LTR/RTL in that configuration, and that is what khtml does. However, 10.6.4: If none of the three are 'auto': If both 'margin-top' and 'margin-bottom' are 'auto', solve the equation under the extra constraint that the two margins get equal values. does not state to solve for zero margin-top. Equal values might not be the most sensible choice given the default top-to-bottom layout, but that is the current specification. => complain to CSS working group.