一、表单submit提交

<form action="" method="post" name="addForm"  onsubmit="return CheckPost();"><!--提交前先验证表单-->
     <div>用户:<input type="text" size="10" name="user" maxlength="20"/></div>
     <div>标题:<input type="text" name="title" maxlength="50"/></div>
     <div>内容:<textarea name="content" rows="8" cols="30"></textarea></div>
     <div>
           <input type="submit" name="submit" value="发表留言"/>
     </div>
</form>

<script language="javascript">
   function CheckPost ()
   {
      if (addForm.user.value == "")
      {
          alert("请填写用户名！");
          addForm.username.focus();
          return false;
      }
     if (addForm.title.value.length ===0)
     {
          alert("标题不能为空！");
          addForm.title.focus();
          return false;
     }
     return true;
   }
</script>

二、button提交

<script language="javascript">
      function SendForm () 
      {
          if(CheckPost()) 
          {
              document.addForm.submit();
              //$("#formid").submit();
         }
      }//提交前先验证表单
 
     function CheckPost () 
     {
          if (addForm.user.value == "") 
          {
                alert("请填写用户名！");
                addForm.username.focus();
                return false;

          }
          if (addForm.title.value.length ===0)
     {
          alert("标题不能为空！");
          addForm.title.focus();
          return false;
     }
         return true;
    }
 </script>
 
 <form action="" method="post" name="addForm" id="formid">
      <div>用户:<input type="text" size="10" name="user" maxlength="20"/></div>
      <div>标题:<input type="text" name="title" maxlength="50"/></div>
      <div>内容:<textarea name="content" rows="8" cols="30"></textarea></div>
      <div><input type="button" name="submit" value="发表留言" onclick="SendForm();"/></div>
 </form>