用户名只能字母与数子
用户注册时限制注册只能字母与数子,并且首字必须是字母

------解决方案--------------------
对了,有个小BUG,改一下
<%
userid=request( "userid ")
mywords= "0123456789qwertyuiopasdfghjklzxcvbnm "
for i = 1 to len(userid)
absword=right(left(userid,i),1)
if instr(mywords,lcase(absword)) <1 then
response.write "验证出错！ "
exit for
end if
next
%>