Rollovers..

I was having a problem with rollovers, even though I do
them in a very conventional way:

function roll(i) {
document[i].src = eval(i + "_roll.src")
} // in which value passed to function is "name" attr in img tag..

but on my home page, www.francesdelrio.com, I have rollovers like this:

function doRoll(Img,newImage) {
Img.src = newImage.src;
Img.width = newImage.width; // what's the point
Img.height = newImage.height; // of these two?
}
function roll_web() {
doRoll(document.web, web_roll);
} // etc.

I'm just trying to remember why I did it like this, it was a solution
given to me by someone in this ng, I believe the problem might have been
that rollovers were not working in Opera (don't have Opera installed
anymore, can't check it out); does this mean all my other rollovers are
not working in Opera? (if you have Opera, can u pls go to
www.francesdelrio.com/resume in Opera and roll over images near top of
page and see if rollovers work? How prevelant is use of Opera? do I
need to always script taking Opera into account?