It means that someone has enable browser detection on your server, or added mobile Safari to the list of detectable browsers. This is usually done to redirect mobile browsers to pages that are better designed for them. With the iPad it can be a good or bad thing. The UI's for these pages are usually designed for small phone screens, that's annoying. But the new pages are also designed to be simpler and avoid some of the code that won't work with mobile Safari, so sometimes this is the only way to make the website work.
If you want the normal web page back get the Atomic browser from the app store.
You can set Atomic to lie about what kind of browser it is, so that your server will give you the full web page again. That does not mean that it really emulates those browsers. Atomic will work, or not, pretty much like mobile Safari. Might be some minor differences in abilities.
To change the browser in Atomic, tap on the gear icon to the left of the URL bar, and choose Identify Browser As.