It's a standard thing that's added to links like this when they come from a server that can be updated using a programming language such as the one it uses, which I think it aspx (as that's microsoft's own language they developed could be asp though same thing really, although x stands for extra so work out what the difference is). When you enter a link it will be msn.co.uk and that extra bit is generated from the server to find the homepage for that site, technically web sites should be something like this: http://www.mypage.com/index.html the extension of index.html refers to the actual file name of the page, which for developers is important when linking pages on a site. This extra bit of code will direct you to the main page, it doesn't come up as filename.extension because the server has generated the page name, rather than the developer. Hope that helps you understand why it's there. It's meaningless really but the server generates it automatically and although it can be removed they tend to leave it in as it's easier that way.

Thank you!