map area with onMouseOver effect

[Martin Nadoll]

Hello

i have a image with a map made of four different areas.

now i want to include a onMouseOver effect.
When the mouse is over one of the four areas (all are rectangles) i want to
make this area visible with a 1px red border around only this particular
area.
And i want to hide the border onMouseOut.

I dont know, how to code that.

Thanks for any help,
Martin Nadoll