On a Mac, in order to SAVE "MyFirstWebPage" created by “Text Edit” as a web page:

• Select Main Menu/Format: 'Make Plain Text'
• Select 'File' -> 'Save'
• Save the file as: 'MyFirstWebPage.html'
• You will be asked if you want to use '.html' ... do that.

On a Mac, in order to EDIT a web page using “Text Edit” :

• Open Text Edit / File / Preferences
• New Document: select “Plain Text” & “Wrap To Page”
• Open and Save: select “Display HTML files