Occasionally you may want to check your internet speed to see if you are getting close to what you are paying for from your ISP. Perhaps you may use Speedtest.net: http://www.speedtest.net/? This is a good site, and I've used it many times. There are others, and I just came across one that is simple, fast, and powered by Netflix: https://fast.com/ . I compared both sites on my download speed, and they're close, but not exactly the same, as you would expect.
However, if you just want a quick test of your download speed, you might give fast.com a try.