Minify the HTML output on the frontend. This will help with pagespeed. On Multisite you may either Network Activate this plugin or you may install it on a case by case basis within the subsites you choose.
Compatible with standard and multisite installations of the wordpress.org software.
It is possible that this may or may-not break some image sliders. If it does, no worries, just simply 'deactivate' the plugin to fix it.