Web Magnifier

I want a tool on my mouse that works the way that old Apple MacOS system 8 did for the viewing impaired: A keystroke triggers the mouse (or a tap on the screen somewhere) to become a big magnifying lens, with the ability to mouse click from within it. When I use the key functions or preferences to make the viewing font bigger, the images and text within those images are still small. Did I miss some function in Firefox that lets me do this?