A quick and little known tip is that you can view Photoshop files (.psd) in Safari. This is great for previewing a design in a browser without having to constantly save out to a jpg. As you can see in the image below is a .psd of a mock up of Inspect Element’s 404 page loaded into Safari. Now you can easily and quickly save your work in Photoshop and switch to Safari to see your work, how want to see it, in a browser.
Unfortunately this is a Mac OS X only feature. I had hoped that Safari 4 on Windows would support it but no luck. A quick search reveals that there doesn’t seem to be a plugin that can replicate this functionality in Firefox which is a shame. Hopefully someone out there is developing one, or planning to!