MB stands for megabyte, which is one million bytes. That’s what the mega prefix represents: 1,000,000
of something. To get an idea of sizes, a 20 or 30 page Word document is only about 1 MB. So a 20MB image is a
large image.
In general, the only reason you’d want image files that big is for high-end photography sites or image sharing
sites like Flickr (www.flickr.com) that really value tons of detail. You don’t need anything like that for a simple
profile picture.