What is the cause of the horizontal scroll bar on my website?

What is the cause of the horizontal scroll bar on my website. How do I get rid of it. Is it because of my tables sizes or a CSS script or the pics too big.please advise. http://www.thailandtravels.co.uk/|||Try moving the picture with source http://www.thailandtravels.co.uk/thaitra鈥?/a> somewhere else, or get rid of it entirely.