背景图片自适应

imgcover

$(function(){ 
    $("body").append("<div id='main_bg'/>"); 
    $("#main_bg").append("<img src='bg.jpg' id='bigpic'>"); 
    cover(); 
    $(window).resize(function(){ //浏览器窗口变化 
        cover(); 
    }); 
}); 
function cover(){ 
    var win_width = $(window).width(); 
    var win_height = $(window).height(); 
    $("#bigpic").attr({width:win_width,height:win_height}); 
}