Bob,
You need to log into Wikispaces.
Here is what happens: once in a while, Wikispaces logs everybody out for security reasons. You need to find the link "Sign In" at the top right corner and enter your username and password again. Once you do it, the page will be unlocked for you!
The way to see if you are logged or not is to look into that top right corner menu. If you are logged, it has your username, and if not, it says Guest.
Cheers,
Maria Droujkova
Make math your own, to make your own math.