Here’s an oldie but a goodie…
When web browsing, my favorite way to scroll down a page is by pressing the “Space Bar“. If you want to scroll up, press “Shift + Space Bar“.
*note: this is the equivalent to hitting either the “page up” or “page down” keys, but i’m rarely on a full sized keyboard that has those as separate keys, and even if there are those keys, it’s more comfortable to just hit the space bar than moving your hand all the way to the right to hit page up or page down…but don’t take my word for it. give it a try and see which method works better for you!
*2nd note: if you’re using Chrome or Safari, this should provide you with nice smooth scrolling up/down. In Firefox, it’s more of a jumping motion. Try it and you’ll see what I mean.