Fix miscellaneous typos involving dashes/hyphens
Add missing space after punctuation
Rewrite p-p. to pp. for consistency
Fix miscellaneous typos involving ; and :
Add missing spaces after commas

git grep -E ',[0-9]' *.html | grep -v -E '[0-9],[0-9][0-9][0-9]'
Remove spaces before commas

git grep -F ' ,'
Hyphenate mid-1961 and mid-1962 for consistency
Use em dash where it seems to belong
Replace '-' with en dash in date ranges (again)

A few were missed...
Replace 1/2 with &frac12; where appropriate
Replace +/- with &plusmn; where appropriate