I was having a big problem with the registration page here on MSVNetwork. When the registration page would load, several of the input text boxes (namely User Name and Password) would change to a yellow background. Since I use white text here, it made it very difficult to read what you were typing. Also, this problem would not occur on all computers.
I finally found the answer. The Google Toolbar. Apparently the Google Toolbar has a feature that allows the user to "auto-fill" certain form fields encountered on the web. User Name and Password being two of them. I found a site that explains the problem and offers a few solutions.
Outsmarting the Google Toolbar