Jquery problem in all IE's but not FF or Chrome

Jquery problem in all IE's but not FF or Chrome

I have this bit of code that works in all browsers except IE9, IE8, IE7. Please Help

$('#stream .main_img').each(function(){
     var h = $('#stream .main_img').height();
     $(this).parent().next('.video-button').css('margin-top', ((h-75)/-2) + "px");
});