I want to achieve a certain distance from the bottom of the pop-up page scrolling div

 1 <script type="text/javascript">
 2   $(window).scroll(function () {
 3         if ($(this).scrollTop() > 100) {
 4             $(".wrap-float").stop().show().animate({ bottom: '10px' }, 300);
 5         }
 6         else {
 7             $(".wrap-float").stop().animate({ bottom: '-430px' }, 300);
 8         }
 9     });
10   $('.wrap-float').click(function () {
11   $(".fast-close").animate({ bottom: '-380px', opacity: '0' }, 500);
12        return false;
13     });
14 
15 </script>

$ A first sliding distance is determined greater than 100, if the implementation of a language;

The second $ is used to close pop, pop because the bottom cover may have content visitors want to see!

.wrap-float 

.fast-close 

is the class name (; class name) 

some marketing websites should need this