Every web developer today faces the challenge of checking website compatibility across a large pool of browsers and browser versions in the marketplace. Up and until now, either you could install every browser, verify the website via a visual inspection and debug with tools specialized to that browser, or you could send a URL to a third-party screenshotting service like BrowserShots for an all-in-one visual inspection.
The former is messy and tedious but gives you more control and an opportunity to diagnose problems, whilst the latter is simple but slow and useless to fix the problem. Long Zheng has shown us SuperPreview is the best of both worlds.
SuperPreview as a tool allows you to compare different rendering engines in a single unified interface. Simple clicks gives you comparisons between Internet Explorer 6, the native version of Internet Explorer installed, other browsers you may have installed locally – Firefox 3.5, Safari 3, Safari 4 – and even an bitmap images of website prototypes.
Source: Expression Web SuperPreview