You can make a tool tip appear anywhere you like using the <acronym></acronym> tags. Suppose you didn't know what W3C meant? Hold your cursor over the blue "W3C" and wait for the little "tool-tip" box to appear.
You can take it to extremes. Hold your cursor over the word "extremes" on the left.
If you "view-source" this file, you will see the message written in the tool-tip box appeared on a LONG single line. This is one of the few places where whitespace counts. You must not put a carriage return within the title attribute itself.