Update class4.html

[jannypie]

Working with instructor during class to review slides 1) First slide on static positioning - left-aligned images so that they reflect actual normal flow with static positioning (were centered) 2) Renamed example classes for clarification; naming the class the same as the property was causing confusion with our students (example: .float { float: left; } changed to .float-example { float: left;} )

--general code cleanup as i was going through to improve readability

[Roenok]

Clearing out some old PRs. We made a bunch of changes to the repo recently; I hope you'll enjoy. Thanks!