Having the same meta decription on all pages is not really good for SEO. Let's take a look how to get rid of these duplicate tags:
Open your template headinclude in the style editor and delete the meta description tag (but copy it into your clipboard first).
HTML Code:
1">{vb:rawphrase page_x, {vb:raw pagenumber}}-{vb:raw foruminfo.description_clean}" />
Delete the meta tag with keywords too - they are useless anyway.
HTML Code:
Now search for {vb:raw headinclude} in all templates. You'll get a list of templates which use the template "headinclude". There are important pages like FORUMHOME, SHOWTHREAD, MEMBERINFO etc. where you might want to add your custom meta description tag.
Open the template FORUMHOME in the editor and find {vb:raw headinclude}. Paste the copied code from the template "headinclude" under {vb:raw headinclude}. After saving there will be displayed unique description that is set in vBulletin options.
Now another template where you want to display a unique description. Here is an example of my description code in the SHOWTHREAD template:
HTML Code:
Hint: Find variables from the TITLE tag (or other parts of a template) and put them in your description to display dynamically generated content like shown above.