The Codes revealed on the outside cover of the book The De Vinci Code.
There were four codes you had to figure out what were they?

Hello.

It seems that there are actually 5 codes associated with things on (or
alluded to by) the cover:

(1) Faint coordinates on the left side of the back cover (37º 57' 6.5" North
77º 8' 44" West) that refer to the location of CIA headquarters and a
statue called Kryptos.

(2) The initials WW  associated with a quote pertaining to Kryptos.

(3) The bold letters in the plot summary on the inside the book flaps spell out:
"Is there no help for the widow's son." 

(4) 'Mason,' the group associated with "Is there no help for the widow's son." 

(5) There's a wheel on the back cover (near the UPC) with the numbers:
20 11 11 68 1 10 11 61 15 5 8 73 11.  The numbers refer to chapter
numbers in the book.  The first letter of each chapter reference: E U
U N R S U P I M L B U  (an anagram of the United State's "E Pluribus
Unum" motto).

sources:

I. Kryptos
II. WW
III.IS THERE NO HELP FOR THE WIDOWS SON
IV. Mason
V. E Pluribus Unum 
source: binarytoybox.com, cached by Google:
http://216.239.57.104/search?q=cache:f5sd781z40EJ:www.binarytoybox.com/archives/000749.html&hl=en&ie=UTF-8

"I want to be Indiana Jones"
http://www.pixelsandwidgets.com/weblogs/archives/000220.shtml

Andrea's Journal
http://www.entropics.net/~tangent/2003_12_01_archive.htm

"Does Langley know about this?"
http://www.ideoplastos.net/blog/archives/000248.html

Matt-thornton.net: Da Vinci Codes
http://www.matt-thornton.net/topics.php?topic=14&subcat=94

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search strategy:
"da vinci code" cover codes
"vinci code", "pluribus unum", "there no help for the"

I hope this helps.