Hello I use a custom validator in my forms, and if there is an error in the input type i load a background image to the input box to indicate there is a problem there. document.getElementById(what).style.backgroundImage = "url('images/error.png')"; document.getElementById(what).style.backgroundRepeat = "no-repeat"; document.getElementById(what).style.backgroundPosition = "left top"; document.getElementById(what).style.paddingLeft = "15px"; This works good in IE, but in Firefox, when i load error.png into the box, it extends the length of the box by the size of the image. No problem in functioning but it makes a bad look. When the error is removed and backgroundImage is cleared it turns back to normal length.