What tools can be used to keep track of changes on web pages?
http://www.readfree.net/bbs/register.PHP (Google translated version: http://translate.Google.com/translate?js=n&prev=_t&hl=en&ie=UTF-8&layout=2&eotf=1&sl=zh-CN&tl=en&u=http%3A%2F%2Fwww.readfree.net%2Fbbs%2Fregister.PHP) is a forum where registration is not available all the time. It says it limits the number of new users for registration every day, and releases openings from time to time.
I wonder if there is some software that can track the website, and notify me when there is opening? Can RSS do that? Note the website is PHP.