<script>
function getimgurl(p) {
return prompt(p,'http://');
}
</script>
<form name="inputform">
<a href="javascript:;" οnclick="document.inputform.IMGURL.value=getimgurl('嘿嘿!哦?')">
点呀!你点呗!</a>
<input name="IMGURL">
</form>