Ad Server Redirect issues
Depending on the ad server you use, URL escape codes may or may not be part of your every day job. As a Google DART for Publishers (DFP) customer, I encountered this issue only a couple of times. However as a Google DART Enterprise (DE) customer I encountered this issue on a regular basis. There are 2 primary issues. Issue 1 is that a url can only have 1 question mark in it. Issue number two is if the value of one of your url parameters contains an ampersand (&) a browser will think that you are declaring a new variable/parameter. In both cases, the solution involves using the URL escape codes found in the table below.

SPACE %20 = %3D
# %23 > %3E
$ %24 ? %3F
% %25 [ %5B
& %26 \ %5C
@ %40 ] %5D
` %60 ^ %5E
/ %2F { %7B
: %3A | %7C
; %3B } %7D
< %3C ~ %7E