On my page I have a problem: selecting elements on class does not work using jQuery. The strange thing is that it does work using document.getElementsByClassName.

1.     jQuery('.ContentMethodIntroduction').css('width', '50px'); //does nothing
       document.getElementsByClassName('ContentMethodIntroduction')[0].style.width='50px'; //works
   
   

How can this be? I thought jQuery uses the same document.getElementsByClassName (when supported)? What can be the cause of this problem?

My page does pass the W3C XHTML 1.0 Transitional validator test.