<script language="javascript">

function CheckEmail(form){
 var email = form.Email.value;
 var pattern = /^([a-zA-Z0-9._-])+@([a-zA-Z0-9_-])+(\.[a-zA-Z0-9_-])+/;
 flag = pattern.test(email);
 if(!flag){
  alert("email格式不正确!");
  form.Email.focus();
  return false;
 }
 return (true);
}
</script>
<form name="form1" onSubmit=" return false;">
请输入email:<input type="text" name="Email" value=""><input type="button" onClick="return CheckEmail(this.form);" value="验证">

</form>