TextEdit is the simplest app to edit basic HTML. If you are editing directly from a webpage, use a right/2-finger click and press view source. Copy the HTML text and paste it into TextEdit. Make any changes you need to make. When you save the document, use the Unicode(UTF-8) Plain Text Encoding option, but use the .html extension in the file name (i.e. index.html). When you press save, a message will pop up asking about your file extension. Press "use .HTML". TextEdit has an option for saving directly as HTML, but it can sometimes cause problems.
