Background image on hover! When does it load?

[bokeh]

If my page contains the following:

#abc:hover {
background-image: url(1.jpg);
}

at what point will that image be loaded?
When the page loads?
Or when the point is first placed over it?

[BonRouge]

On hover.
You can fix that by putting the image in the html but styled so that it's invisible.

http://bonrouge.com/br.php?page=rollover2