This site uses several unique tools for working with the math stuff. Running a couple of quick checks may save you some frustration. Most every "fix" is a very small download and a simple install.
Download
I strongly recommend Mozilla's FireFox web browser. The recommended display setting is at least 1024 X 768.
Check if you have the Adobe Flash plug-in. More than likely you do, it's installed on 96% of the world's computers.
Click on the "Show Me" link.
You should see a simple animation of some lasers.
If you do not, click on the Adobe Flash Player logo to the left and follow the download and installation instructions.