In Internet Explorer, moving my mouse over an image (that has the ALT="something" specified), brings up a tooltip with the word "something" there.

Question 1: From what version of IE onwards was this feature present? Is it present in Opera?

Question 2: A toolbar I've created consists of about seven to eight images of size 16*16. This means I haven't written any words there. For example, an image of a question mark, and it's got the tooltip "help." Now I just checked it in Mozilla, and mozilla has no tooltip!! I'm assuming Netscape doesn't either? Any suggestions as to an alternative? How can I inform the (stupid) user that this question mark image is for "help"?

THanks.