I just installed this image-zoom add on for FireFox:
formatting link
it allows you to zoom in on images that are embedded in web pages. Of course the zoomability is limited by the inherent resolution of the image, but a lot of images have untapped resolution to be exploited. Really nice for getting a better look at eBay pix. Or DropBox pix.
No, I am not spamming or phishing. If you don't trust the link, don't go there.
Bob