这是什么类型的CSS？

I was looking at an old installation of mediawiki which is not rendering css properly the code in the Chrome Dev Tools is showing CSS like this

{{{border-width|1}}}px solid {{{titleborder|{{{border|#ababab}}}}}}

Not able to understand what is the pre-processor used and why its not working. Can someone hint to some direction.

Here in the image the span text is not rendered as a blue bar since The CSS breaks because of the template code. Not sure where to look for this CSS Template issue. Isnt much aware about the Media Wiki Architecture.

enter image description here

Most likely, this CSS is used inline in a template on your page.

{{{border-width|1}}} means “use the value of the parameter border-width, or 1 if none is given”. In this case, the parameters to the template are not expanded. There are a number of possible reasons, though until you show us the template code, or give us a link to the page, we can only guess:

  1. Syntax errors in the template (like a missing bracket somewhere, or a stray <nowiki> tag)
  2. A complex template chain passed the expansion depth limit.
  3. Too many templates on one page (surpassing the post-expand include size)

You can check the category Category:Pages containing omitted template arguments to see if it is any of the latter, though I strongly suspect the first.

Edit: Also, before doing anything else, you can try to simply purge the page, to re-render it.

Edit2: Now that we have a screenshot, it looks like some wikicode that an extension could have thrown in there. Start by disabling all extensions, and, if that helps, enable them again one by one.