Under your hat
There are plenty of privacy features in Firefox 3.5. Everybody might call it Porn Mode, but Private Browsing is a feature in Internet Explorer 8 and Firefox can't afford to be without it. Whether you'll ever use it depends on what kind of sites you decide to browse.
You can also choose to wipe your history for a certain amount of time - perhaps a couple of hours - or even forget just the site you have just visited. This option is accessed via your History viewer (it's a right-click option) and enables you to cover your tracks should you have just bought a present for somebody, for example.
One of the most interesting features of Firefox 3.5 is integrated geolocation, where you can permit Firefox to store details of your current location. In time, this will enable sites to bring you search results, maps or other local services depending on where you are. Beltzner says this could also "do something cool that we haven't even thought of yet".
Finally, Firefox 3.5 adds support for other HTML 5 improvements including downloadable web fonts and CSS improvements are also supported.
If the download figures for Firefox 3.0 are anything to go by, the release of 3.5 should have interesting implications for the browser wars - 3.0 was downloaded 8.3 million times in its first 24 hours online in June 2008.