very language develops its own set of conventions and grammar rules. A few years before the web boom I saw HyperLand, a BBC program about many of the conceptual aspects of hypermedia. Surprisingly, this program is still relevant and I recommend it to anyone interested in multimedia. What struck me the most were the discussions on developing a grammar for interactive media. As a comparison it described early cinema. The language used in the first movies was basically the same as in theater; it took a while special techniques such as jump cuts, flash backs and close-ups were invented by early cinematographers and accepted by their audience. Today you could probably fill books with film grammar. In many respects hypermedia is in the same situation as cinema was in its early days.

But there is no standard way in HTML to differentiate links

In HTML we use many of the rules from the print industry such as making titles big and bold, indenting lists and emphasizing in bold. But there is no standard way in HTML to differentiate links. So the only hint as to what will follow a link are the high-lighted words themselves or their immediate surroundings.
As a web user and a web designer, I have often been frustrated by the fact that I don't know what will follow a link. Is the link going to be a description, a definition, a whole web site on the topic or just a footnote? Also there is no way of knowing what will happen "physically". Will my browser jump to a new page, another part of the page or will it pop-up a new window? It's confusing, and I may very well hesitate to pursue links that I might have found very interesting or useful.
I have been trying to find solutions to these problems. One option is to write a very clear description of the link content, something like: "See a page explaining how to use tables to control lay-out in html". Now, this can work in an index but it would be very disturbing in the context of a running text. Another option is to use a little JavaScript that lets you control the contents of the status bar. So when you rollover a link you can give a little better explanation in the status bar of what is to follow if you click. This solution is not very elegant as it forces the reader to look down at the edge of the browser window.
Another option is to vary the appearance of different types of links. I have decided to render all my glossary links in italics and in a color that does not contrast too much with the text color. This is to keep the emphasis on more important links. Adding an asterisk could signal a footnote*. My hope is that, as users get used to this system they will spontaneously know if they want to follow a link or not, waste less time and effort and ultimately be happier with their visit.
As HTML evolves we might see a "type" parameter added to the anchor tag.