I am a computer consultant. I have taken classes on HTML and I have reviewed the XML and HTML 4.0 specifications. My ideas are very early in development. Tags that are not displayed such as keywords, signatures etc. would be added at the end of the file. OK, there's no reason why you shouldn't rewrite the HTML DTD to do this.
Tags are the things that mark the start and end of elements.
These protocols would probably be used by HTML editors. The event tag would list all the tags in the HTML file with rough descriptions so the browser knows what to expect. For example, someone mentioned the problem with loading tables. The HTML editor could calculate the impact of size elements in the table tag. It would add a stream tag to points in the table.