if  (checknamestr(window.userform.text1.value)  &&  checkpwdstr(window.userform.password1.value)  &&  checkemailstr(window.userform.text2.value)  &&  checkoicqstr(window.userform.text3.value)  &&  checktelstr(window.userform.text4.value))      
 
当checknamestr(window.userform.text1.value)返回的结果不是true时,if的条件肯定是false了,后面的也不会执行。  
把checknamestr函数里的这一段  
if  (flagi==i)  
{  
alert(  "username  successful!  ");  
return;  
}                          
里的return  改成return  true再试一试