Setting the width of both the textbox (ie. input type=\"text\") and the textarea to 500px doesn\'t work in IE6 and Chrome, only works fine in FF2 (haven\'t tested other browsers
You might have some luck using a set of reset styles in your CSS. They go a long way to eliminating the cross-browser differences between the way elements are rendered.
Eric Meyer (one of the web's best minds on CSS) describes reset styles and why he uses them here -- with his latest version here.
That said, without knowing the overall effect you're trying to achieve, form elements are notoriously difficult to style in a way that is perfectly consistent across browser platforms. Best of luck. :)