Don't Start Anything You Can't Finish!
With few exceptions, all tags in HTML have an opening tag
<tagname> and a closing tag </tagname>.
In XHTML, you must provide a closing tag for every opening
tag that requires one.
Some browsers are forgiving if you omit the closing tag, but
don't expect the same results from all browsers! To aid yourself
in finding mistakes, it is recommended that you first view your pages
with less-forgiving FireFox.
