The new structural elements in HTML5 include section, article, aside, hgroup, header, footer, nav, figure, figcaption, time, and mark.
First, let’s look at support in Internet Explorer. Starting in version 9 of IE, there is support for all the new elements. Versions prior to that provided no support, not even partial.
Other browsers have been supporting these elements for some time. Firefox support extends back to version 6. Firefox is currently at version 9. Chrome, now at version 16, has supported these HTML5 elements since version 13. Safari provided partial support before version 5. Full support began in version 5. Safari’s current version is 5.1. As for Opera, partial support began in version 11, full support in 11.1. Opera is currently at 11.6.
On the mobile side, iOS has supported everything since iOS4. iOS is currently at version 5. Even iOS3 had partial support. Opera Mini is providing partial support in the current version 6. However, Opera Mobile has offered full support since version 11.0. Opera Mobile is currently at 11.5. Android versions 2.2 and above, including the current 2.3/3.0, have full support.
When only partial support is provided, you can use CSS to declare a display:block rule for all the new elements and workaround the problem.
Check out HTML5 Please for information about current support (and workarounds) for everything in HTML5.