web page layout

[shivvy]

My cat has just stood on my laptop keypad and messed up the look of webpages I am viewing! I think I have it all back to normal apart from the sides of the pages. There are large white/blank areas down both sides of the open page. It looks as if the part with writing or pictures on it is not wide enough to fill the window. I hope that makes sense to someone! If so, can you advise on how to right it please?
Thanks.