You set style and language options in the Style & Language Settings screen of vBulletin Options.
Following are the Style and Language settings.
Default Language (default: English(US))
You must click Save for changes to take effect.
Select the default language for your site. This language is used for all guests, and any members who have not expressed a language preference in their options.
Select the default style for your site. This style will be used for all guests, and any members who have not expressed a style preference in their options, or are attempting to use a style that does not exist or is forbidden.
Default Style for Mobile Browsers
Select the default mobile style for modern mobile browsers. This style is used if a user is browsing your site with a modern mobile browser. Set to None to use a desktop browser style.
Default Style for Old Mobile Browsers
Select the default mobile style for old mobile browsers. This style is used if a user is browsing your site with a modern mobile browser. Set to None to use a desktop browser style.
Allow Users to Change Styles (Yes/No)
Whether or not users can set their preferred style when they register or when editing their user options. Setting this to No forces users to use whatever style has been specified for the site.
Location of clear.gif (default: clear.gif)
Enter the path of your clear.gif image, relative to your site base directory.
By default, the value of this setting is clear.gif, meaning that the image is located in the base directory of your vBulletin installation (in the same folder as forumdisplay.php).
The URL must be relative, NOT beginning with http://.
Store CSS Stylesheets as Files? (Yes/No)
If you want to store the CSS stylesheet for each style as a file, you must ensure that you have a directory called vbulletin_css inside the clientscript folder, and that the web server has permission to write and delete files in that directory.
Use 'vBMenu' DHTML Popup Menus? (Yes/No)
Whether or not to use dynamic HTML popup menus to reduce screen clutter if the user's browser allows it.
Disabling this option will also disable some AJAX features, such as user name suggestion.
Use Legacy (Vertical) Postbit Template (Yes/No)
If you prefer the postbit style that uses two vertical columns rather than the horizontal layout, you can revert to using that template with this switch.
If you enable this option and want to customize the template, edit the postbit_legacy template rather than the postbit.
Show Instant Messaging Program Icons (Yes/No)
Whether or not to show the images for Skype, ICQ, AIM, MSN, and Yahoo! Messenger if the user has entered the correct information in his/her profile. These links are shown in various places throughout the site, for example on posts, who's online, memberlist, and profile.
Use SkypeWeb Graphics (Yes/No/Use Language-Specific SkypeWeb Graphics)
If set to Yes, the Skype™ icon from the SkypeWeb server is used to show users' online status.
If set to No, the local (static) graphic is used.
If set to “Language Specific”, graphics in the language being used by the visiting user are loaded. If the Language Specific option does not work, switch it off and try again in a few weeks.
Search Engine Referrers
Enter one or more HTTP referrer addresses as a search engine source. Enter multiple referrer names on separate lines.
For the most accurate detection, enter only the essential part of the domain. For example, instead of entering "www.yahoo.com" and "www1.yahoo.com", enter ".yahoo.com", or, better yet, “yahoo.”. Instead of entering ".google.com", ".google.ca", ".google.co.uk", enter ".google.".
Alternatively, if you are interested in only part of the domain, you can use an asterisk (*) as a wild card. For example "search*" will match "searching.site", "searchmaster.site", etc.