Jared Wein of Mozilla blogged last month about a new feature he was developing for Firefox 14 called "click-to-play".
The idea is to block the default loading of plugins like Java and Flash when surfing to reduce the memory footprint and provide protection against exploitation of plugin vulnerabilities.
Firefox 14 click-to-play featureFirefox 14 click-to-play featureIf you have ever used NoScript, ScriptNo or Flashblock you will be familiar with this idea.
When you load a page like YouTube that has an embedded Flash/PDF/Java object, instead of it instantly loading the video you will see a black box with a logo representing the plugin.
When you click on the box it will launch the plugin and the video or other content will be rendered.