I have an external style sheet with this in it:
.box {
padding-left:30px;
background-color: #BBFF88;
border-width: 0;
overflow: hidden;
width: 400px;
height:
You should use window.getComputedStyle to get that value. I would recommend against using offsetWidth or clientWidth if you're looking for the CSS value because those return a width which includes padding and other calculations.
Using getComputedStyle, your code would be:
var e = document.getElementById('0');
var w = document.defaultView.getComputedStyle(e,null).getPropertyValue("width");
The documentation for this is given at MDC : window.getComputedStyle