<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <style> #test { box-sizing: border-box; width: 100px; height: 100px; padding: 10px; } </style> </head> <body> <div id="test"></div> <script src="../../jquery.js"></script> <script src="../iframeTest.js"></script> <script> startIframeTest( jQuery( "#test" ).css( 'width' ) ); </script> </body> </html>