Looking to auto scale site for smaller screens

Hello All,

I am racking my brain and have tried everything with no no such luck. My site is http://www.craigmurwaycfc.com and I currently have the width set to 999px but really liked it at 1100px wide (looks better on larger screens) but would be too large on netbooks and such. I found .content_full{width:90%;} to add to the child theme but that did not work. Any recommendations? Thanks!