Changes following content team review

H4s changed to H3s for better navigation. Minor grammatical changes and a few rogue errors introduced by various content editors removed.
changes following review by content team
changes following content team review
Merge pull request #82 from BenClancy/patch-6

Changes following content team review
Merge pull request #83 from BenClancy/patch-7

changes following review by content team
Merge pull request #84 from BenClancy/patch-8

changes following content team review
Fix bad markup