For many web developers cross browser testing has been a pain. One of the greatest pains has been test the different versions of IE, 5.5, 6, 7 and now 8. Users of browsers like Firefox, Safari and Opera tend to upgrade regular and even in some cases the updates are automated.
The reality however is that IE still controls the majority share in the browser market thanks to Microsoft dominance of the Operating System found on personal computers around the world.
Here is a good tool for testing different versions of IE.
Here are some reviews
Go ahead and give it a try. Solving those CSS and JavaScript errors should be alot easier now.