class1 - Formatting and tag/validation fixes
class2 - Cleanup for typos, quotes, validating markup, style, extraneous tags, matching example code to actual markup.
class3 - Validation, quotes, indentation and other formatting fixes (esp. for large code blocks), extraneous tags
class4 - quotes, line breaks, validation, comments, indentation, and code sample formatting for space
Merge pull request #1 from EliseWei/common-updates

Structural updates
Merging conflicts between pull requests
Clean up errors introduced in previous merge
correct class number for class 4
Merge pull request #3 from sabreuse/class-cleanup

Clean up errors introduced in previous merge
Merge pull request #2 from girldevelopit/master

update