解决底部问题

<script type="text/javascript">
// Window load event used just in case window height is dependant upon images
$(window).bind("load", function() {
var footerHeight = 0,
footerTop = 0,
$footer = $(".copy");
positionFooter();
//定义positionFooter function
function positionFooter() {
//取到div#footer高度
footerHeight = $footer.height();
//div#footer离屏幕顶部的距离
footerTop = ($(window).scrollTop()+$(window).height()-footerHeight)+"px";
//如果页面内容高度小于屏幕高度，.copy将绝对定位到屏幕底部，否则.copy保留它的正常静态定位
if ( ($(document.body).height()+footerHeight) < $(window).height()) {
$footer.css({
position: "absolute"
}).stop().animate({
top: footerTop
});
} else {
$footer.css({
position: "static"
});
}
}
$(window).scroll(positionFooter).resize(positionFooter);
});
</script>