Actually, you are quite right when it comes to header/footer. Here is some basic information on how each of the major HTML5 tags can/should be used (I suggest reading the full source linked at the bottom):
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CodeMagic Tinymce plugin
About CodeMagic is an advanced source code editor plugin for Tinymce. It integrates CodeMirrorlibrary for syntax coloring and Jsbeautifier library for code formating and indentation.