| status codes | The response codes sent by a server whenever a link is clicked, a webpage or file is requested, or a form is submitted. Common HTTP status codes important to SEO: |
| feed reader | A browser add-on program that gathers and displays feeds according to the users preferences and subscriptions. |
| wordpress plugin | A plugin to a feature capabilities to a wordpress installation. |
| pay-per-click | or PPC: Online advertising approach that determines the cost of an ad by the number of people who click on the ad. |
| opt-in | Marketing initiatives in which a user chooses to participate. For example, an opt-in newsletter requires the user to input an email address in order to opt-in and receive the newsletter. |
