Cookies are an important tool for tracking a users interactions with a web site over time. Unfortunately, due to bad press relating to their usage, they are often blocked by users leading to a reduction in the accuracy of the collected data. Because using the Internet has become hard to do without having first party cookies enabled, it’s now best practice to use these in a tracking application.
However, this is only possible when the data is being transmitted back to the same server from which the page being viewed originated. This is often a problem when creating a third party tracking service, or when using a global domain to collect data for a portfolio of sites. Luckily, there are techniques that can be used to overcome the problem.