vBulletin Manual - Adding or Editing a Prefix

Path to add new prefixes: Topic Prefixes > Topic Prefix Manager > click Add Prefix next to the Topic Prefix Set

Once you have created a prefix set, you may add any number of prefixes to that set. If a thread has a prefix applied to it, the prefix will show anywhere the thread title shows. For that reason, you must define two versions of the prefix: a plain text version and a rich text version. See below for more information.

The following options are on the page for adding/editing a prefix set:

Prefix ID - This is the unique identifier for this prefix. Only one prefix can have this value and the value may only contain A-Z, a-z, 0-9, and _ (underscores) only. It will be the id used in the URL to select other threads with this prefixid. Once you pick a prefix set id, you will not have a chance to change it (it will not be editable when editing the prefix set).
Prefix Set - The set this prefix is to be placed in. This prefix will only be selectable in forums that have this set enabled. If you change this set, topics that can no longer use this prefix will have it removed!
Title (Plain Text) - This is the title of the prefix, using no special markup. This will be shown in the prefix list menu, when the topic title is shown in the navigation bar, or when the topic title is used in an email. example - For Sale
Title (Rich Text) - This is also the title of the prefix, but you may use HTML to add additional markup to the title. This version of the prefix will be shown in a list of topics and within the thread itself. example of a red prefix title - <span style=”color: red;”>For Sale</span> - which will display as For Sale
Display Order - The sort order for this prefix. Lower values will be displayed first within the selected prefix set.

If the topic title is a link to view the topic, the prefix will generally not be linked. However, the prefix will be included in the link if the topic title is used in the navigation bar.

Prefixes will also be placed directly before a thread title, with only a space separating them. For this reason, you will probably want to include something to make the prefix stand out from the title. In the rich text value, this could be color, italics, or an image (For Sale). However, in the plain text version, you may need to include a colon or square brackets ("For Sale:" or "[For Sale]").