function check_form(){if(document.getElementById('title').value==''){alert('主题不能为空');return false;}if(document.getElementById('f_name').value==''){alert('姓名不能为空');return false;}if(document.getElementById('f_mail').value==''){alert('E-mail不能为空');return false;}if(document.getElementById('f_tel').value==''){alert('电话不能为空');return false;}if(document.getElementById('f_content').value==''){alert('内容不能为空');return false;}}