When images have a watermark then that means that they are (copy) protected and you need to contact the site and possibly buy the image to get one without the watermark.

If you are getting very different results in Firefox and IE, you could try disabling Firefox's use of hardware acceleration for graphics.

orange Firefox button (or Tools menu) > Options > Advanced

On the "General" mini-tab, uncheck the box for "Use hardware acceleration when available"

This will take effect when you restart Firefox.