set rs=server.CreateObject("adodb.recordset")
rs.open "select * from [表] where [字段]='"&LCase(trim(request.form("name")))&"'" ,conn,1,1
if rs.recordcount>0 then
response.write "<script language=javascript>"
response.write "alert('对不起,已经有此用户名,请重新输入!');"
response.write "this.location.href='vbscript:history.back()';</script>"
Response.end
else