Textcelerator is a browser plugin that helps you speed read on web pages. It works with Firefox and Chrome, and adds a window like this one for speed-reading on every web page. It's free for 30 days, then costs $45. You're reading at 300 words per minute now, but with a little practice, you could be reading over a thousand words per minute!
You might want to adjust the speed. Click on the arrows next to the speed indicator on this window, or press '[' (left bracket) to slow down and ']' (right bracket) to speed up. You can also pause and resume by pressing 'p', and use the arrow keys to go forward and back, if you missed something. Finally, you can also click on a word to jump to it.
The technique you're using now is called Moving Serial Visual Presentation, which is a modified version of a speed-reading technique called Rapid Serial Visual Presentation, which shows each word in the same spot instead of moving up and down. The motion helps your mind keep track of what order words go in, and keeps you from missing words. Textcelerator also highlights negation words, so you won't miss them, no matter how fast you're going. It adjusts the amount of time each group of words is shown based on a prediction of how long you'll take to absorb it.
Textcelerator is available as a browser extension for Google Chrome. Once installed, it will be added to all pages. It's free for 30 days, after which you can buy it for $45.