key=request.querystring("key")
st="abcdefg"
if instr(st,key)>0 then
  response.write "key包含在st中"
end if

------解决方案--------------------
VBScript code
key=request.querystring("key")
st="abcdefg"
if len(key)=6 and instr(st,key)>0 then'增加判断长度
  response.write "key长度为6并且key包含在st中"
end if

------解决方案--------------------

1、
VB code
<%
dim str,key,st
st="asdfb"
str=Request.ServerVariables("Query_String")
if left(str,4)="key=" or instr(str,"&key=")>0 then
    key=split(str,"key=")(1)
    key=split(key,"&")(0)
    if len(key)=6 and instr(st,key)>0 then
        Response.write "key参数长度为6且在st字符串中"
    end if
else
    Response.write "根本就没key参数"
end if
%>