Have you ever opened your email inbox finding an email saying the site you were just working on has an issue? While this happens all of the time for designers and developers for the web, and will for years to come, developers have just gone into Internet Explorer to find the problem which didn't exist in today's standards-compliant browsers (Safari/Chrome, Firefox, Opera, etc...). For a developer on the Mac or Linux platforms, opening IE is not as much of an ease as if you had a Windows computer right next to you.
Seeing before believing
So, you have that email saying you overlooked a design flaw or operability issue on your site. What's next? The hardest thing for me as a developer is trying to fix an issue I can't see. While screenshots from clients can sometimes cut the mustard when finding the issue, it still doesn't solve the issue nor does it help in your many attempts at making that bug fix.
The question becomes, how do you test your site in browsers you don't have? One solution is load your computer with every version of every browser you can, from the nightly builds to the old versions you keep in the archive.
For example, in my applications folder on my Mac, I have 6 versions of Mozilla's Firefox ready for duty, each of them only usable when the other versions are not running, you have to reset all of the settings and check for updates (which you don't want). When it comes to other browsers such as Apple's Safari, you can't downgrade to a lower version as the browser is tangled into the operating system.
While having a locally running copy of each browser configuration at hand would be the solution to this, you can get similar results with browser screenshot websites:
Browser Shots (http://browsershots.org/)
The daddy of the screenshot sites is Browser Shots. It offers on-demand screenshots of your site in any of a number of browsers on a number of platforms (not just windows/linux/mac/etc...). The site is free (advertisement based) and can take hours for some of the more popular browsers to load but it allows you to get pretty much any screenshot. Run the batch, come back in 29 minutes to find a few of them done, extend your screenshot request (it is only open for 30 minutes by default) and keep going.
NetRenderer (http://ipinfo.info/netrenderer/)
Netrenderer provides the 4 most requested screenshots you probably will need (assuming you are not on a PC), the Internet Explorer versions of 5.5, 6, 7, and 9 (with IE9 beta once it is released). The bonus of the netrenderer is it is instant, no waiting, no queues, no hassle, just the screenshot you want when you want it. The problem here is the limit of only IE, so you need to try another site for those specialty browsers in linux.
Alkaline (aka Litmus) (http://litmusapp.com/alkaline/)
If you want to pay for a convenient way to test windows browsers on your mac without the waiting, the folks at Salted Services created Alkaline (used to be called Litmus, now a email compatibility app). It offers the iPhone app and a downloadable app for your mac to test on those 17 Windows browsers they say are most relevant.
Adobe Browserlab (https://browserlab.adobe.com/)
Now part of the CS5 suite, the once free online beta allowed users to fireup the resource heavy flash site which would process IE screenshots but the site now allows more features and ties right into Dreamweaver if it is your choice of development platform.
