Why do I get the layout alongwith the ajax result

Why do I get the layout alongwith the ajax result

I am using Ajax to search some posts tagged under some word. What I am
using is just an input; no form. The event is onKeyUp so ajax request is
made when there is a keyup.
Result: The ajax do send back a response.
Problem: The layout is also sent back. When I am even using the code
Layout = null; too.
Language I use: I am using ASP.NET Web Pages.
What I have tried: I have tried to search for some corrections, first I
was not using the layout for the page, then I was told to use Layout =
null; to make sure, the layout is not used for the code.
But now the layout is sent back, whether I use this or not.
Other wise the code is perfect! You can have a look at the layout issue here:

The logo and all this nav menu is provided under the main page. Almost
just above the footer where the result has to be pasted! But instead of
posts or some query, the layout is being posted back.