You can remove your tags by clicking the X on the tags you wish to remove from the feature you added them to. For example, if you have added tags to your Custom Status Dropdown, Job Categories, or to particular jobs:
Job Categories in Careers Page (Account Details)
Custom Status Dropdown in Workflow (Account Details)
Tags added to individual active and offline jobs (Edit job page)
Once the tags are removed from where they were entered, the system will remove them from the instances to which they were applied (it may take a few minutes for them to disappear).