This extension is useful when you use PivotX in multisite mode. Multisite Transparent makes the links to resources like images and CSS files much cleaner for a site that is run by PivotX in multisite mode. It transforms http://example.org/pivotx/sites/example.org/images/file.jpg to http://example.org/images/file.jpg.
NB! This extension is incompatible with Minify. If you enable "Use Minify in Frontend", this extension will do nothing.