A while ago I gave the impression that the hgroup element was no longer part of the HTML specification, this is not the case at least for the moment. (January 2014) W3C still lists this element as part of the specification. You can also access the ongoing discussion regarding the possible changes/replacement for hgroup also at W3C.
Should it stay part of the specification here is how to use it:
The hgroup element is used to group headings together. It must contain at least two of the heading elements and no other information. It is for grouping a title with a subtitle. It can contain different combinations such as <h1> with <h2.> or <h3> with <h4> etc.
For those of you that create headings with display: inline ( to get rid of the unsightly gap) and then add a <br> you will not longer be able to do this because it will not validate if a <br> is inside an hgroup. You need to play with the margins inorder to reduce the gap.
Attributes: All Global