例如:
我们在百度中搜索 ，则网址后面的参数就是
http://www.baidu.com/s?cl=3&wd=%BD%C5%B1%BE%D6%AE%BC%D2

如果我们想将%BD%C5%B1%BE%D6%AE%BC%D2还原为中文，使用下面的函数即可。
<%
response.write urldecode("http://www.baidu.com/s?cl=3&wd=%BD%C5%B1%BE%D6%AE%BC%D2")
'================================================
'函数名：URLDecode
'作 用：URL解码
'================================================
Function URLDecode(ByVal urlcode)
Dim start,final,length,char,i,butf8,pass
Dim leftstr,rightstr,finalstr
Dim b0,b1,bx,blength,position,u,utf8
On Error Resume Next

b0 = Array(192,224,240,248,252,254)
urlcode = Replace(urlcode,"+"," ")
pass = 0
utf8 = -1

length = Len(urlcode) : start = InStr(urlcode,"%") : final = InStrRev(urlcode,"%")
If start = 0 Or length < 3 Then URLDecode = urlcode : Exit Function
leftstr = Left(urlcode,start - 1) : rightstr = Right(urlcode,length - 2 - final)

For i = start To final
char = Mid(urlcode,i,1)
If char = "%" Then
bx = URLDecode_Hex(Mid(urlcode,i + 1,2))
If bx > 31 And bx < 128 Then
i = i + 2
finalstr = finalstr & ChrW(bx)
ElseIf bx > 127 Then
i = i + 2
If utf8 < 0 Then
butf8 = 1 : blength = -1 : b1 = bx
For position = 4 To 0 Step -1
If b1 >= b0(position) And b1 < b0(position + 1) Then
blength = position
Exit For
End If
Next
If blength > -1 Then
For position = 0 To blength
b1 = URLDecode_Hex(Mid(urlcode,i + position * 3 + 2,2))
If b1 < 128 Or b1 > 191 Then butf8 = 0 : Exit For
Next
Else
butf8 = 0
End If
If butf8 = 1 And blength = 0 Then butf8 = -2
If butf8 > -1 And utf8 = -2 Then i = start - 1 : finalstr = "" : pass = 1
utf8 = butf8
End If
If pass = 0 Then
If utf8 = 1 Then
b1 = bx : u = 0 : blength = -1
For position = 4 To 0 Step -1
If b1 >= b0(position) And b1 < b0(position + 1) Then
blength = position
b1 = (b1 xOr b0(position)) * 64 ^ (position + 1)
Exit For
End If
Next
If blength > -1 Then
For position = 0 To blength
bx = URLDecode_Hex(Mid(urlcode,i + 2,2)) : i = i + 3
If bx < 128 Or bx > 191 Then u = 0 : Exit For
u = u + (bx And 63) * 64 ^ (blength - position)
Next
If u > 0 Then finalstr = finalstr & ChrW(b1 + u)
End If
Else
b1 = bx * &h100 : u = 0
bx = URLDecode_Hex(Mid(urlcode,i + 2,2))
If bx > 0 Then
u = b1 + bx
i = i + 3
Else
If Left(urlcode,1) = "%" Then
u = b1 + Asc(Mid(urlcode,i + 3,1))
i = i + 2
Else
u = b1 + Asc(Mid(urlcode,i + 1,1))
i = i + 1
End If
End If
finalstr = finalstr & Chr(u)
End If
Else
pass = 0
End If
End If
Else
finalstr = finalstr & char
End If
Next
URLDecode = leftstr & finalstr & rightstr
End Function

Function URLDecode_Hex(ByVal h)
On Error Resume Next
h = "&h" & Trim(h) : URLDecode_Hex = -1
If Len(h) <> 4 Then Exit Function
If isNumeric(h) Then URLDecode_Hex = cInt(h)
End Function
%>