I understand the purpose of the sheet. Again:

What happens if you load up internet explorer (or another web browser) and try and access one of the sites in your sample? Try:
http://miami.craigslist.org/brw/pts/3949953392.html

What happens if you run this code:
Sub test()
Dim rng, lr As Long, a, res As String, x As Long
lr = Cells(Rows.Count, 1).End(xlUp).Row
rng = Range("a2:b" & lr)
x = LBound(rng)
With CreateObject("MSXML2.XMLHTTP")
    .Open "GET", rng(x, 1), False
    .setRequestHeader "Content-Type", "application/x-www-form-urlencoded"
    .send rng(x, 1)
    MsgBox .responsetext
End With
Range("a2:b" & lr) = rng
End Sub
Do you get a messagebox? What does it say?