User-Agent: Mozilla/5.0 (compatible; Konqueror/4.3; Linux) KHTML/4.3.1 (like Gecko) Build Identifier: By setting a :visited background image, the firefox history can be sniffed easily. I was curious how easy it is and managed to write a history sniffer in just 64 lines of Python (see the URL), so you really might want to fix the issue quickly. Please remove the optimization of only loading required css data based on the visited info! I didn't find my original bug report, so I add this one with more backup: To load anything depending on the state of the history exposes private information. Reproducible: Always