I recently learned from my highly valued Wise Women friends that the source of my yellow form fields was the Google Toolbar. I had been searching my HTML and my CSS for some explanation as to why my form had yellow backgrounds in some of the text fields. Turns out that the Google toolbar (which I like and am not knocking) has an autocomplete option in the Options area. If autocomplete is turned on, the Google toolbar indicates form fields which it will autocomplete by making them yellow. This also explains the mystery of why the form fields looked yellow in Windows but not in Mac, as the Google toolbar doesn’t work in Mac browsers.