render your XHTML invalid, and must be replaced by their named entities
"&", "<", and ">".
+Keep line lengths within 108 characters so that additions or changes are easy to view in github pull requests.
+Code examples that are supposed to be all one line are an exception in which case the <pre></pre> tag should be
+used to to tell the browser to display the code as one line.
3. Custom classes
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