What is P3P?
To understand if you should have P3P enabled for your tracking links, first you need to know what it is. The Platform for Privacy Preferences Project (P3P) enables websites and tracking platforms to express their privacy practices in a standard format that can be retrieved automatically and interpreted easily by user agents such as web browsers. P3P allows browsers to be informed of your website and tracking link privacy practices in both machine- and human-readable formats. In turn, this allows for the automation of certain decision-making functions within the consumers' browser, thus eliminating the need to read the privacy policies at every site they visit.
Why is P3P necessary?
P3P provides descriptions that describe the collection and use of privacy data from your tracking link or website. Browsers can then develop a predictable behavior when blocking content like tracking cookies. Some tracking systems, such as LinkTrust, use P3P to make their practices explicit and thus open them to public scrutiny. However, this is not true of all tracking providers. It is important to note that tracking providers do not generally make your links P3P compliant by default. This little step will increase your tracking accuracy by allowing more of your tracking cookies to be written to the consumers' browser when your links are clicked.
How do I know if my tracking links are P3P compliant?
It's simple. Visit http://www.w3.org/P3P/validator.html, enter your complete tracking URL and click "Check". If your links are not P3P compliant, contact your tracking or website provider and request it. I requested it for my tracking links and LinkTrust had them compliant the same day.
Digg 
