I found this in a few different places around the 'net - hopefully it's helpful:

Use AutoComplete to Enter Addresses Faster in Internet Explorer 6

The AutoComplete feature in Internet Explorer 6 can fill in the prefix and suffix of Web addresses so all you must enter is the name.

• Just type the name in the address bar and hold down the Control key while you press Enter. Internet Explorer 6 automatically adds the http:// and the www. and the .com.

For example, click in Address bar and type MSN, and then hold down the Control key and press Enter. Internet Explorer 6 will go to the address http://www.msn.com