Error: 'window' is undefined

I get an error message when I try to open the script;

Line: 10
Char: 1
Code: 800A1391
Source: Microsoft JScript runtime error

What am I doing wrong?

To install scripts you need to be using the Firefox web browser and have the Greasemonkey add-on installed. Once you have both of these, try installing the script again.

I have Firefox and Greasemonkey and still get this error message. What else could it be??

After you restart your browser, go back to the page were you found the script and click the link again and a dialog will popup to install the script.
Don't download the script to your computer itself and try installing it from there; it won't work.

Oh right, that makes sense then -- I was confused about this error. Although...

Don't download the script to your computer itself and try installing running it from there; it won't work.

You can install a script from your computer, however you will need to open it with Firefox to do this.