                        課程
                    
                        /前端開發(fā)
                        
                            /jQuery
                        
                        /jQuery基礎(chǔ)課程

請問為什么實現(xiàn)不了

<!DOCTYPE?html>
<html>
<head>
????<title></title>
????<script?src="http://idcbgp.cn/data/jquery-1.8.2.min.js"?type="text/javascript">
</script>
<script?src="http://idcbgp.cn/data/jquery-ui-1.9.2.min.js"?type="text/javascript"></script>
<script>
????$.fn.extend({
????????changecolor:function({
????????????$.(this).bind("hover",function({
????????????????$.(this).css({"background-color":"red"});
????????????}))
????????})
????????});
????????$.("ul?li").changecolor();
????????
</script>
<style>
????li?a:link,li?a:visited{
????????text-decoration:none;
????????color:gray;
????}
????li?a:hover,li?a:active{
????????text-decoration:none;
????}
</style>
</head>
<body>
<div?>
????<ul>
????????<li><a?href="#">今天星期二</a></li>
????????<li><a?href="#">明天星期三</a></li>
?????
????</ul>
</div>
</body>
</html>

哪里錯了，求指教~