1 <script type="text/javascript">
 2 jQuery(document).ready(function() {
 3 var topmenu = $(".main_tab");
 4 var topmenu_top = topmenu.offset().top;
 5 reset_topmenu_top(topmenu, topmenu_top);
 6 jQuery(window).scroll(function() {
 7 reset_topmenu_top(topmenu, topmenu_top);
 8 });
 9 });
10 function reset_topmenu_top(topmenu, topmenu_top) {
11 var document_scroll_top = jQuery(document).scrollTop();
12 if (document_scroll_top > topmenu_top) {
13 topmenu.css({'position':'fixed','top':'0px'});
14 // topmenu.css({'border-style':'solid','border-width':'2px','border-color':'#000'})//控制边框
15 // topmenu.css({'background':'#ff0000'})//控制背景
16 }
17 if (document_scroll_top <= topmenu_top) {
18 topmenu.attr('style',{'top':topmenu_top+'px'});
19 // topmenu.css({'background':'green'});//控制背景
20 }
21 }
22 
23 </script>