Introduction
I have read that using extensions to HTML (particularly done in the past by Netscape and Internet Explorer), e.g. moving and layered text, scripted dynamic documents, absolute text- and image positioning - is discouraged because if you use a non-standard HTML tag (such as the extensions), you are excluding a particular part of your audience.
An old solution to this could be, make an initial home page with two buttons "I use FireFox"/"I use Internet Explorer". I believe this choice is now made in JavaScript, embedded in the header (but what if the user blocks JavaScript? I suppose show a message "you need JavaScript").
And so, let your browser do the formatting, you focus on the content and stick to standard HTML. So it seems to be the purpose of HTML.
This is especially true when your document may look glorious on your browser but very ugly on others.
The Question
Is it best not to use extensions for these reasons, or has the Web 2.0 advanced enough so that these problems no longer exist?
