They are save to use according to caniuse.com/#feat=html5semantic.
Use 'header' and 'footer' semantic HTML5 elements. They are save to u…
…se according to http://caniuse.com/#feat=html5semantic
I'm still not entirely certain on the "safe-to-use" bit; IE8 (eww) requires the Shiv and behaves, uh, "interestingly" without it.
I thought IE8 would not be used any longer, but I just took a look at
and saw that IE8 still has a market share of 6.6% worldwide (interestingly, in China about 26%).
Ok, so this should probably not be included.
I expect IE8 to die in another decade or so, remembering that WinXP could only go up to IE8. When it's usage share drops below 5%, I'd say semantic elements will be "safe to use". In this case, however, I suggest jumping the curve; I'd guess all our users use functional (for a very forgiving definition of 'functional') web browsers so this won't be an issue, really.
The site template has since been completely revamped. Thanks tho!