I'm not sure if I understand the question.
Can you write hypertext in emacs? Yes. It's basically the same as if you were to write HTML in Windows Notepad. It's just text.
Is emacs a WYSIWYG editor for html? Most definitely not. All you will see is straight text for tags, elements, attributes, etc.
Is there an emacs mode for hypertext? I would think so, but I don't know of any off-hand. An emacs mode might colorize the text, do character matching (like < and > for instance), automatically frame multi-line comments, and nifty things. You'll have to search for one if this is what you're after. There may be one included by default for HTML. Just save the file with a ".html" suffix, and open it in emacs to see if it changes to HTML mode.