If I may quote the ‘Alternative browsers pose challenge for cybersleuths‘ article by C|Net:

Internet Explorer hides nothing from police and other investigators who examine PCs to discover which sites the user has visited, according to a class held Wednesday at the annual training meeting of the High Tech Crime Investigation Association. Investigators know the location of the IE browser cache, cookie files and history, and they know how to read those files. Also, popular forensics tools can help out.

But that story changes when it comes to alternative Web browsers such as Firefox and Opera, instructor Glenn Lewis said at the well-attended session. These programs use different structures, files and naming conventions for the data that investigators are after. And files are in a different location on the hard drive, which can cause trouble for examiners. Furthermore, forensics software may not support the Web browsers, he said.

Where’s a :smilie_hitting_brick_wall: icon when you need one? 🙄