Using multiple versions of browsers (IE + FF)

Internet Explorer

I found this handy tool, IETester, for testing your websites in multiple versions of IE, each in a different tab. Currently it can test IE 5.5, 6, 7 and 8 beta.

Since it's an early alpha release there is a list of known bugs on their homepage but it is good enough to view pages in.

Firefox

I found the easiest way of testing in various versions of FF was to use a portable version since it doesn't need any installation and won't mess with whichever current install you have.

You can find all portable legacy versions if FF here.

Firebug for all browsers!

When designing websites I've found firebug for FireFox invaluable for checking out exactly what's going on. I've now found you can get Firebug lite for use on any browser!

It's very easy to use, all you have to do is include the following code in any page that you want to use it in:

<script type="'text/javascript'" src="%27http://getfirebug.com/releases/lite/1.2/firebug-lite-compressed.js%27"></script>

Genius.