GPLv2 description could do with comma about its variants

"There are multiple variants of the
 GPL each with different requirements"

Without a comma, this passage has no break where it would
be used to add the hint of nuance between GPL versions.
Merge pull request #149 from randomecho/gplv2-comma

GPLv2 description could do with comma about its variants
Refactor header.html's properties.
Use a space in replace function.
Remove IE 6/7 hacks.
Use double quotes.
Specify box sizing.