What is causing the <span tag to show when you click one of the arrows below?
This Contents page exhibits a problem with extension CategoryTree.
This problem behavior showed up here when I dump my teflpedia wiki database -- I'm testing an upgrade of http://teflpedia.com from MW 1.22.2 to MW 1.31.1 -- into this test wiki here. The arrows worked find till I dumped my teflpedia (MediaWiki 1.22.2) database into this test wiki (and yes I ran maintenance/update.php with no issues).
It shows some kind of dynamically generated <span style="color:#0645AD;">►</span> tag that is non selectable in the browser, yet is displayed in the page instead of being invisibly interpreted as it should be.
While checking Special:AllMessages (specifically all modified messages) I noticed I had <span color in the three pages that define the arrows. Removed the <span tags on these three pages and the problem vanish! :)
Click the arrows to expand or close page list
Click one of the below arrows ( ▼ or ► ) to expand and close the tree branches.