Edges of the web on the screen

[jesusca]

Hello
Can you help me?, How to get the header photos of a website does not leave a small separation in the left and right of the screen?.
I want it to look good glued to the screen edges with no small separation.
I tried to adjust the page, the photos but I can not.

Can you help me?

you can see what I explain in the attached image


Thank you very much