I use Firefox as a browser (and recommend it to all) and it has a whole pile of extensions available to make doing whatever easier for the user. One of them is called "Image Zoom"
http://imagezoom.yellowgorilla.net/ and it lets me easily enlarge or reduce the size of any image by just right-clicking and moving the mouse-wheel. It is a whole lot easier than any of the alternatives when looking at pix that are a little to small or large for easy viewing, and it lets me examine the pix in greater detail than would otherwise be possible without starting up some other program outside the browser.
I wanted to bring this useful tool to the attention of those who use Firefox (or Mozilla) and suspect there may be comparable add-ons available for other browsers. Anyone who knows how to achieve similar image re-sizing in other browsers might want to add that info here.