That gives you plain text tooltips. If you want rich tooltips, with formatted HTML in them, you'll need to use a library to do that. Fortunately there are loads of those.
<span title="This will show as a tooltip">Mouse over for a tooltip!</span>
<a href="http://www.stackoverflow.com" title="Link to stackoverflow.com">stackoverflow.com</a>
<img src="something.png" alt="Something" title="Something">