<head runat="server">
<title>无标题页</title>
<script type="text/javascript">
function aa(id)
{
if(document.getElementById(id).style.display=='block') //此处为判断，定用双等号，如果使用单等号将会造成可隐藏，无法显示。且语法也是错误的
{
document.getElementById(id).style.display="none";
}
else
{
document.getElementById(id).style.display="block";
}
}
</script>
</head>
<body>
<form id="form1" runat="server">
<div>
<div ><a onclick="aa('aa')" href="#">点我</a></div>
<div id="aa" style="background-color:red;display:block">sfdsdaf</div>
//一点要加上此DIV的样式display，否则当页面首次加载div是显示，需点击2此才能达到隐藏效果
</div>
</form>
</body>
</html>
<title>无标题页</title>
<script type="text/javascript">
function aa(id)
{
if(document.getElementById(id).style.display=='block') //此处为判断，定用双等号，如果使用单等号将会造成可隐藏，无法显示。且语法也是错误的
{
document.getElementById(id).style.display="none";
}
else
{
document.getElementById(id).style.display="block";
}
}
</script>
</head>
<body>
<form id="form1" runat="server">
<div>
<div ><a onclick="aa('aa')" href="#">点我</a></div>
<div id="aa" style="background-color:red;display:block">sfdsdaf</div>
//一点要加上此DIV的样式display，否则当页面首次加载div是显示，需点击2此才能达到隐藏效果
</div>
</form>
</body>
</html>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<title>div显示和隐藏切换</title>
<script language="javascript" type="text/javascript">
function DivShow() {
var obj = document.getElementById("div1");
if(obj.style.display == "none") {
obj.style.display = "block";
}
else {
obj.style.display = "none";
}
}
</script>
</head><body>
<a href="#" onclick="DivShow();">点我</a><br />
<div id="div1">我就是div</div>
</body>
</html>