One of the greatest problems with CSS, or Cascading Style Sheets, is the issue of cross browser compatibility. What may look great in Mozilla browsers looks terrible in Internet Explorer, and may totally break in Netscape. The biggest mistake a web designer or developer using CSS can make is to design for only one browser, or to assume that since the largest group of viewers use IE, to disregard its flaws that are apparent in other browsers.
Cross Browser Issues: CSS Hacks, Understanding Compatibility - Know the Browsers (Page 2 of 5 )
there are so many other browsers, such as Mozillaís browser project Camino for Mac, Maxthon, Konqueror, and many more that do support CSS 2.1. Honestly, there are simply just too many to list and analyze, when in actuality most of them are based on the technologies of the major players I mentioned; for example, Maxthon is based on IE; and if it works on Firefox, itís very likely going to work on Mozilla and Camino. Browsers that generally do not support CSS 2.1 will not be covered here, like text-based Lynx and older browsers.
Mozilla and Firefox
The Mozilla Group makes the open-source Gecko browser engine, used by the Mozilla browser suite and by a diverse range of products. Gecko is highly standards-compliant and is available on many platforms. Firefox is a Mozilla browser. Mozilla based browsers like Firefox were the earliest browsers to support CSS fairly well.
Safari for Mac
Safari is an OS X browser using a variant of Konqueror's KHTML browser engine. Apple reportedly chose to base Safari on KHTML instead of Gecko for three reasons:
KHTML was faster, KHTML's source code is smaller and cleaner, and Apple doesn't need Gecko's multi-platform support. Overall this browser behaves the same as Mozilla. Some minor tweaks might be needed to be made to a style sheet to accommodate proper rendering, but overall this browser will handle content like Mozilla with regard to your style sheet.
Opera Software makes the Opera browser for many operating systems, including embedded systems. Opera is renowned as a browser that is small, fast, standards-compliant, and available on many platforms. Opera fully supports CSS 2.1. So when validating your CSS code, you can be sure that your validated CSS will render properly in Opera, either with the strict doctype or in quirks mode.