Along the lines of "don't roll your own" and "don't reinvent the wheel," instead of Javascript, you could use the HTML attribute that is already defined to provide just the functionality you're trying to replicate: namely, the title attribute (and not alt, which is a whole 'nother beast, though Internet Explorer thinks otherwise). So,

<a href="example.com" title="This is my title. There are many like it, but this one is mine. My title is my best friend.  It is my life.  I must master it as I master my life.">

BCE
--You'reYour culture will adapt to service our'sours.