Do not edit the Twenty Eleven theme. First create a child theme for your changes. Or install a custom CSS plugin.
installation done child theme and Css plugin…
Plzzzz How Give Css Cording For Grid Layout
I’m sorry but it is really beyond the scope of these forums to deal with general CSS issues. Try a dedicated CSS resource such as http://www.css-discuss.org/ instead. In the meantime, try using Firefox with the Firebug add-on for this kind of CSS work. Or use whatever developer tool is available in your web browser.
http://getfirebug.com/
