It is the usual problem of incompatibility among browsers and especially of IE. These days, are far less in many regards, if I remember what was the case back in 2005, where we were developing webpages manually and it could take a substantial time to test them, in a cross browser fashion. But unfortunately there are still differences in the render model regarding html 5, css and Ecmascript - the latter have been substantially been limited. You can use frameworks like jQuery and many other and there are cross - tools and libraries for css too, for cross - browser compatibility and even for compatibility between mobile and web pages. As, web development has got a lot more complicated and demanding, I think it is not a good recommendation to try developing things manually any more. Use ready - to - go tools, to be on the safe side - of course a good working knowledge of the programming / scripting / mark-up languages and technologies is still a must, for any serious developer.