Okay so I just downloaded the Firefox web developer tool and did a CSS validation on my site. It shows 12 errors, but I am still none the wiser what they mean or how I fix, anyone about to help me, my shop is live and I hope no one visits whilst this layout is messed up.

156 HR Value Error : border-bottom Lexical error at line 156, column 35. Encountered: ";" (59), after : "#" ;
159 HR Value Error : border-bottom Parse error - Unrecognized }
188 #mainWrapper Value Error : border Lexical error at line 188, column 28. Encountered: ";" (59), after : "#" ;
189 #mainWrapper Value Error : border Parse error - Unrecognized }
405 #productDescription, .shippingEstimatorWrapper Parse Error #cartAdd {; padding: 1em;
406 #productDescription, .shippingEstimatorWrapper Parse error - Unrecognized }
409 .tableHeading TH Value Error : border-bottom Lexical error at line 409, column 35. Encountered: ";" (59), after : "#" ;
410 .tableHeading TH Value Error : border-bottom Parse error - Unrecognized }
545 .centerBoxWrapper Value Error : border Lexical error at line 545, column 28. Encountered: ";" (59), after : "#" ;
546 height Value Error : border Parse Error height: 1%;
547 margin Value Error : border Parse Error margin: 1.1em 0;
548 margin Value Error : border Parse error - Unrecognized }