There are times when you need to keep an eye on a website. You might need to know if the text on a page has changed, or if a new article has been published. Going back to visit the site every day or so might not be that practical and if there is a change being able to see the differences can save you from a lot of headaches.
There are several sites offering this kind of service out there, but personally I’ve found ChangeDetection.com to be incredibly useful
It does what it says on the tin – it detects changes and when it finds them you get notified via email.