用jquery<script type="text/javascript">
$(document).ready(function() {
$('#btn').click(function() {
$('#img').attr('src', 'your image src');
});
});
</script>
$(document).ready(function() {
$('#btn').click(function() {
$('#img').attr('src', 'your image src');
});
});
</script>
http://api.jquery.com/ready/click event:这里是点击按钮的事件
http://api.jquery.com/click/attr function: 修改一个element的attribute的值，这里是就该img element的src 的值。
http://api.jquery.com/attr/
<head runat="server">
<title></title>
<script>
function Test() {
if (document.getElementById("bgImg").style.backgroundImage.indexOf('Jellyfish.jpg') > 0) {
document.getElementById("bgImg").style.backgroundImage = "url('bg_img.jpg')";
}
else {
document.getElementById("bgImg").style.backgroundImage = "url('Jellyfish.jpg')";
} }
</script>
</head>
<body id="bgImg" > <form id="form1" runat="server">
<div>
<input type="button" id="btn" onclick="javascript:Test();" value="更换" />
</div>
</form>
</body>
</html>