A raw document with all its embedded tags can quickly become nearly unreadable, like computer-programming source code. We strongly recommend that you use comments to guide your composing eye.
Although it’s part of your document, nothing in a comment, which goes between the special starting tag comment delimiters, gets included in the browser display of your document. You see a comment in the source, as in our simple HTML example, but you don’t see it on the display, as evidenced by our comment’s absence. Anyone can download the source text of your documents and read the comments, though, so be careful what you write.