//判断是否为合法email的函数
//调用方法：<input name="email" type="text" class=input1 id="email" onChange="return isEmail(this);" size="50" maxlength="100">
function isEmail(email)
{
 if(email.value.length!=0)
  {
    if (email.value.charAt(0)=="." || email.value.charAt(0)=="@"|| email.value.indexOf('@', 0) == -1 ||   email.value.indexOf('.', 0) == -1 || email.value.lastIndexOf("@")==email.value.length-1 ||   email.value.lastIndexOf(".")==email.value.length-1)
     {
      alert("Email的格式不正確！");
      email.focus();
      return false;
      }
   }
 else
  {
   alert("Email的不能为空！");
   email.focus();
   return false;
   }
}