Can I make text appear when mouse hovers over a hyperlink?

[Gonkski]

I want to have text appear (like a tooltip) when you place the mouse cursor
over a hyperlink. I've added ALT text, but that just shows up before the
graphics load. Is there any way to add these "pop-up" descriptions?

 

[David Bartosik]

It's called a tool tip.
refer to http://www.publishermvps.com/WebDesign/Advanced/tabid/97/Default.aspx