InStr() needs 3 parameters
InStr(CharToStartAt,String,TextToFind)
So your wanting to use InStr(1, List1.List(a), websitein2) Then
code:
For j = 0 To List1.ListCount - 1
If InStr(1, List1(j), websitein2) Then
s = ""
s = s + Mid$(List1(j), InStrRev(List1(j), "-") + 2)
s = Replace(s, "http://", "")
End If
Next j