function checkform(form) 
{ 
if (form.username.value == "") 
{ 
alert("请填写登录名！"); 
form.username.focus(); 
return (false); 
} 
if (form.username.value.length<3) 
{ 
alert("登录名太短！"); 
form.username.focus(); 
return (false); 
} 
if (form.username.value.length>15) 
{ 
alert("登录名太冗长！"); 
form.username.focus(); 
return (false); 
}
if (form.password.value =="") 
{ 
alert("请填写登录密码！"); 
form.password.focus(); 
return (false); 
} 

if(form.password_sure.value==""){ 
alert("请输入您的确认密码！"); 
form.password_sure.focus(); 
return (false); 
} 
var filter=/^\s*[.A-Za-z0-9_-]{6,20}\s*$/; 
if (!filter.test(form.password.value)) { 
alert("密码填写不正确,请重新填写！可使用的字符为（A-Z a-z 0-9 _ - .)长度为6-20个字符。"); 
form.password.focus(); 
form.password.select(); 
return (false); 
} 
if (form.password.value!=form.password_sure.value ){ 
alert("两次填写的密码不一致，请重新填写！"); 
form.password.focus(); 
form.password.select(); 
return (false); 
} 

if (form.Question.value == "") 
{ 
alert("请输入密码保护问题！"); 
form.Question.focus(); 
return (false); 
}
if (form.Question.value.length<4) 
{ 
alert("密码保护问题太短！"); 
form.Question.focus(); 
return (false); 
} 


if (form.Answer.value == "") 
{ 
alert("请输入密码保护答案！"); 
form.Answer.focus(); 
return (false); 
}
if (form.Answer.value.length<4) 
{ 
alert("密码保护答案太短！"); 
form.Answer.focus(); 
return (false); 
} 
}