The @ symbol in front of some strings

[dynamic_sysop]

yep exactly, just saves the fingers a little
but ...
You can also use the / slash instead of the \
eg:

[COLOR=Blue]private void[/COLOR] button1_Click([COLOR=Blue]object[/COLOR] sender, System.EventArgs e) 
        { 
            [COLOR=Blue]string[/COLOR] path = "C:/Documents and Settings/den/My Documents/My Pictures/twins.jpg"; 
            System.Diagnostics.Process.Start( path ); 
        }