The DOM and Compliant Browsers
There is no such thing as complete cross-browser compatibility. I doubt there ever will be, even though the differences between browsers become smaller every year. The W3C DOM is responsible for much of this compatibility, and most browsers have implemented support for both the Core and HTML APIs. This includes Mozilla/Firefox, Netscape Navigator (6.0 and above), Internet Explorer (6.0 and above), Safari, Opera (7.0 and above), Camino, and others.
However, not all aspects of the DOM are implemented equally among all the browsers; as discussed in Chapter 6, Internet Explorer (neither 6.x nor 7+) does not support the DOM Level 2 event model. There are also individual differences in support for CSS, as well as object methods and properties that differ between the browsers.
Most of the compliance issues are subtle, with minor variations in support. They are enough, however, to require testing of any effect using the DOM APIs to ensure it looks good or works as expected with all of your target browsers.
Another variation is more of a minor annoyance than anything. ...