When citing web sites or pages which may change it's important to make a note of the date you accessed the page or retrieved information from the page, and also note the URL of the page. You will need this information for your references.
Websites can sometimes be difficult to cite as you might have to draw information from different areas of the webpage or website to put into your citation. Some information, like authorship or publication date can be hard to find or identify. Scroll to the bottom of this page to see two brief video tutorials that give you some useful tips on where to look for information to make your citation as complete as possible.