by default, firefox buttons and input fields are ugly Windows-95-style - this does not look good at all in a modern GNU/Linux environment IMHO; so I did a wee bit about it; the google.com index page looks like this for me now:

This was a simple matter of feeding firefox some new default css — I put the following code into ~/.mozilla/firefox/*/chrome/userContent.css:

button, input[type=submit], input[type=reset] {
    background: -moz-Dialog;
    color: -moz-DialogText;
    border: 1px outset #CCC;
}

input:not([type]), input[type=password], input[type=text], select,
input[type=file], textarea {
    background: -moz-Field;
    color: -moz-FieldText;
    border: 1px inset #888;
}

I haven't found a way to style the buttons which are part of input[type=file] and select yet.