Will this lens fit my dslr?

I'm thinking of buying this lens http://www.amazon.co.uk/...000O161X0/ Will it fit on a Nikon d3100?

Off course not - what on earth would make you think that a lens made for a nikon camera would actually fit a nikon camera?

Of course it will. Its a Nikon lens made for Nikon cameras.

Here is a complete listing of all Nikon lenses compatible with your D3100:
http://www.nikonusa.com/...index.page

Of course only Nikon AF-S lenses will auto focus on your D3100.

It fits a nikon camera

No, if it was a Canon or Pentax lens it would fit your camera, but those Nikon lenses will not fit your Nikon.

… Whew…