I deleted my own question, https://apple.stackexchange.com/questions/34705/problems-when-connecting-to-wifi-with-the-ipod (the link is for 10k users), because I discovered that the problem is the wireless router that needs to be replaced.
When I deleted the question, the background didn't change.
I don't think it's a problem with the browser because, when I undeleted the question, the page has been refreshed; the same didn't happen when I have deleted the question.
In the case this makes any difference, I am using Safari 5.1.2 running on Mac OS X 10.7.2 (the computer is a Mac Mini).