eviltwit on "Sizing Background Image with Widget in Misty Sadish"

HI - I'm totally new to CSS and generally have no idea what I'm doing.

But, I found a code to put in the txt widget to custom my background image in Misty Sadish without needing the upgrade.

Here it is.

<div style="position:fixed;top:0;left:0;background:#fff url('URL_of_image');width:100%;height:100%;z-index:-1000;"></div>

My question is, is there any way to make it so my background looks fine on every monitor size - by tweaking this code in the txt widget?? I just don't need to deal with the upgrade right now - I've already spent way too much time customizing my blog as it is. If this isn't possible, that's okay. I really like how my blog looks on my screen at least, I guess.

I have a 15.4 screen (1280x800) - if that helps.

Thanks,

paikea