Trackers can contain any alphanumeric characters.
You can separate different elements inside a tracker with an underscore or dash.
Here is an example of a default CrakRevenue link using trackers:
In the example above, DEFAULT is the default tracker.
(We encourage you to change the DEFAULT tracker to something unique for every new campaign — otherwise it gets confusing!)
For instance, an example of a custom tracker might look like this:
In the example above, JUNE_2015_topright is the chosen tracker to indicate the month of promotion, the year, and in this case, the positioning of the link or banner (this is handy to reference later on).
Remember, if you don’t change or create new trackers, there’s no way for you to differentiate your traffic sources.
Read more here: