加在网页上的代码:
验证码(*):

请在验证码框输入 "验证码,看不清楚?请点击刷新验证码" 否则不能留言,谢谢合作!


加在服务端的判断语句:错误信息将以弹出窗口提示返回!

if request("verifycode")<>session("GetCode") then
%>

<%
Response.End
End if

把以下代码复制保存为:GetCode.asp文件,并放在留言页面的目录里.

<%
Option Explicit
Response.buffer=true
Response.Expires = -1
Response.ExpiresAbsolute = Now() - 1
Response.Addheader "cache-control","no-cache"
Response.AddHeader "Pragma","no-cache"
Response.ContentType = "Image/BMP"

Call Com_CreatValidCode("GetCode")

Sub Com_CreatValidCode(pSN)

Randomize

Dim i, ii, iii

Const cOdds = 3 ' 杂点出现的机率
Const cAmount = 10 ' 文字数量
Const cCode = "0123456789"

' 颜色的数据(字符,背景)
Dim vColorData(1)
vColorData(0) = ChrB(0) & ChrB(0) & ChrB(211) ' 蓝0,绿0,红0(黑色)
vColorData(1) = ChrB(255) & ChrB(255) & ChrB(255) ' 蓝250,绿236,红211(浅蓝色)

' 随机产生字符
Dim vCode(4), vCodes
For i = 0 To 3
vCode(i) = Int(Rnd * cAmount)
vCodes = vCodes & Mid(cCode, vCode(i) + 1, 1)
Next
Session(pSN) = vCodes '记录入Session
' 字符的数据
Dim vNumberData(9)
vNumberData(0) = "1110000111110111101111011110111101001011110100101111010010111101001011110111101111011110111110000111"
vNumberData(1) = "1111011111110001111111110111111111011111111101111111110111111111011111111101111111110111111100000111"
vNumberData(2) = "1110000111110111101111011110111111111011111111011111111011111111011111111011111111011110111100000011"
vNumberData(3) = "1110000111110111101111011110111111110111111100111111111101111111111011110111101111011110111110000111"
vNumberData(4) = "1111101111111110111111110011111110101111110110111111011011111100000011111110111111111011111111000011"
vNumberData(5) = "1100000011110111111111011111111101000111110011101111111110111111111011110111101111011110111110000111"
vNumberData(6) = "1111000111111011101111011111111101111111110100011111001110111101111011110111101111011110111110000111"
vNumberData(7) = "1100000011110111011111011101111111101111111110111111110111111111011111111101111111110111111111011111"
vNumberData(8) = "1110000111110111101111011110111101111011111000011111101101111101111011110111101111011110111110000111"
vNumberData(9) = "1110001111110111011111011110111101111011110111001111100010111111111011111111101111011101111110001111"
' 输出图像文件头
Response.BinaryWrite ChrB(66) & ChrB(77) & ChrB(230) & ChrB(4) & ChrB(0) & ChrB(0) & ChrB(0) & ChrB(0) &_
ChrB(0) & ChrB(0) & ChrB(54) & ChrB(0) & ChrB(0) & ChrB(0) & ChrB(40) & ChrB(0) &_
ChrB(0) & ChrB(0) & ChrB(40) & ChrB(0) & ChrB(0) & ChrB(0) & ChrB(10) & ChrB(0) &_
ChrB(0) & ChrB(0) & ChrB(1) & ChrB(0)

' 输出图像信息头
Response.BinaryWrite ChrB(24) & ChrB(0) & ChrB(0) & ChrB(0) & ChrB(0) & ChrB(0) & ChrB(176) & ChrB(4) &_
ChrB(0) & ChrB(0) & ChrB(18) & ChrB(11) & ChrB(0) & ChrB(0) & ChrB(18) & ChrB(11) &_
ChrB(0) & ChrB(0) & ChrB(0) & ChrB(0) & ChrB(0) & ChrB(0) & ChrB(0) & ChrB(0) &_
ChrB(0) & ChrB(0)

For i = 9 To 0 Step -1 ' 历经所有行
For ii = 0 To 3 ' 历经所有字
For iii = 1 To 10 ' 历经所有像素
' 逐行、逐字、逐像素地输出图像数据
If Rnd * 99 + 1 < cOdds Then ' 随机生成杂点
If Mid(vNumberData(vCode(ii)), i * 10 + iii, 1) Then
Response.BinaryWrite vColorData(0)
Else
Response.BinaryWrite vColorData(1)
End If
Else
Response.BinaryWrite vColorData(Mid(vNumberData(vCode(ii)), i * 10 + iii, 1))
End If
Next
Next
Next
End Sub
%>