Here's a shot of a portion of a form on IE without the Google toolbar...
and then with the Google toolbar...
As you can see, the Google toolbar has gone and set the background of fields it can auto-fill to a shade of yellow which is quite dramatically different from the blue that we were using on the original fields. Given the number of people who have one sort of toolbar or the other installed, you can see why this is going to be quite a headache for developers.
There's an excellent post on how to work around this problem at http://code.jenseng.com/google/ - but to summarise, if the look of the form is critical, then you can mark the
!importantto force the toolbar into not modifying it. Your attribute would end up looking something like