0 Top 3 Solutions when your Magento Categories are not displaying

Here are 3 quick solutions to try if you do not see your Magento store categories after a fresh install of Magento or an upgrade to the latest version. I wanted to post this because I just recently helped install Magento for someone (one of my 5 free Magento installations) and experienced this. The installation version was the latest Magento version, 1.2.1.2 and product categories did not show up on the frontend after they were added in the administration interface.

The top 3 solutions to this in my experience are:

1. The categories not added as sub-categories of the Default, Root category.
2. The Magento store configuration has no default category set.
3. The category cache requires a refresh.