There is a group of people getting around the idea of having a Universal Edit Button in browser bars to indicate when a page is editable. The green pencil icon is similar to the orange "broadcast" RSS icon that indicates there is an RSS feed available.

For now, you would have to install a Firefox extension that makes this icon appear in your address bar when a site provides the link tag with type "application/x-wiki" as follows:

<link rel="alternate" type="application/x-wiki" title="Edit" href="[PUT YOUR EDIT URL HERE]" />

Seems like a very good idea to me. I've grown accustomed to using the RSS links in the browser bar rather than searching all over the page for it. Browsers have done a good job of allowing users to leverage this link tag and easily subscribe to RSS feeds. I don't see any reason why wikis and other editable CMS shouldn't provide this as well.