/^(d*.d{0,2}|d+).*$/
hansir给出的测试代码如下：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<title>无标题文档</title>
<script type="text/javascript">
function checkPrice(me){
if(!(/^(?:d+|d+.d{0,2})$/.test(me.value))){
me.value = me.value.replace(/^(d*.d{0,2}|d+).*$/,'$1');
}
}
</script>
</head>
<body>
<input type="text" onkeyup="checkPrice(this);"/>
</body>
</html>