If you have been following the creation of HTML5 via the developers Whatwg.org than you will understand that where was apparently meant to be a <dialog> tag, this was was going to be aimed at providing dialogs / chat logs between users and readers, Microsoft have asked for this feature to be removed from the HTML5 markup and Whatwg.org have listened. There has been a public outcry for the <dialog> tag to included in the next release of HTML, you can see some of the very valid points HERE.

We can only hope that Whatwg can develop a similar tag / element as the dialog had quite a large following, anyhow we will keep you updated once more news comes to hand.