Fix: solve most IGB layout issues.
Fix: solve most IGB layout issues.

Chromium 3.0 doesn't know about <section>, <header> or <nav> and needs
to be told they are block elements.

wffurr/osmium,copyliu/osmium,copyliu/osmium,osmium-org/osmium,copyliu/osmium,osmium-org/osmium,wffurr/osmium,osmium-org/osmium,wffurr/osmium,osmium-org/osmium,wffurr/osmium