Grid header CSS not applied to Firefox.

Hi, I have a grid attached to dhx window, when view in IE8 css applied in Grid Header, but not getting applied when view in Firefox, I am new to DHX kindly help sort this issue.
------------Sample Code-------------
mygrid = w3.attachGrid();
mygrid.setImagePath("/dhtmlx/dhtmlxGrid/codebase/imgs/");
mygrid.setHeader(“Book Title”, Count");
mygrid.setInitWidths(“220,*”);
mygrid.setColAlign(“left,right”);
mygrid.setColTypes(“ed,ed”);
mygrid.setColSorting(“str,str”);
mygrid.init();
mygrid.setSkin(“dhx_skyblue”);
mygrid.parse(griddata,“json”);

Unfortunately we cannot reproduce this issue locally. Please check example here dhtmlx.com/docs/products/dht … _grid.html