[MACCAWS] IE use of ALT tag

Could someone please clear up this for me. I've understood that the way IE 
displays ALT tags on images is wrong (i.e. on mouseover) - the correct 
usage should be title as Opera does.

Before I shoot my mouth off at the RNIB people I just want to be sure.

I know I could look it up but I'm sure that someone here knows.

Regards

john