Simple question from a newbie!

Ok, I am looking to take a picture of a t-shirt with my digital camera and then take it into PS and remove the background. I have found the way to do this part of it, but my question is once I remove the background and add my shadow what is the best way to save the image for the web and get the best response time. I am going to have like 1000 of these throughout my site so I want make sure I do this right and get the best performance.

Thanks so much.

save as JPG or GIF and see how much compression the image can take without looking like sh*t.

When you say compression, what do you mean exactly... How can change the compression of the image... I know this sounds dumb, but I am really new to this stuff.

Thanks.