One of the strong points of web design/development is browser compatibilities. A site that may look like heavens on IE (Internet Explorer) may look the other way on another browser. As a good design pratice, it is therefore required for developers to test their designs on various browsers to see what it looks like. The problem with that however is that it is not that possible to have the numerous different browsers on your system. In fact, it is practically not possible to have two different versions of IE on a Windows OS. And here is where browsershots comes in. Browsershots (http://browsershots.org) let you see how your design looks in over 43 browsers. Just put the link of the site in it and submit. Depending on the number of current requests, you will be put in a queue while the screenshots are being uloaded. All you need do is refresh the result page intermittently to see the screenshots as they are uploaded or wait till your queue time elapse to see all the screenshots. What's more, you can download all the screenshots.
While browsershots answers browser compatibility as regards design, browser compatibility as regards functionality when it comes to client scripting, with javascript especially, is another thing. And to that, the way round it, as far as I know, is using a standard framework that have been tested across browsers by the developer. Personally, I recommend prototypejs (http://prototypejs.org). It is hoowever not a bad idea to keep a couple of browsers on your machine - atleast the most used ones like IE, Firefox and Opera to test designs before they even go online.

other frameworks (just google for them):
scriptaculous, mootools, jquery, YUI - for the most part, these have all built upon prototype and offer in many instances, richer features. Of course, the foundation for all these libs is prototype

kehers:

One of the strong points of web design/development is browser compatibilities.
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It is hoowever not a bad idea to keep a couple of browsers on your machine - atleast the most used ones like IE, Firefox and Opera to test designs before they even go online.

Yup. Very true. I test with IE6, IE7 and FF. There are emulators that enable you run 6 & 7 together. For benefit of the thread you can find such using Multiple IEs (Win Xp only)

Yep a good idea is to have atleast 3 very popular browsers around when developing your website/web app.i personally have 4 that i test with.IE,firefox,opera,netscape.You can add safari to the list if you wish.firefox i believe is the most standards compliant browser out there and i advice developing with firefox before going ahead to test with IE and the rest of them.You should not have much probs with IE 7 cos browser quirks have been greatly taken care of in this version.

mine looks pretty much the same!