This is pretty simple, it merely "types" your text/html onto the webpage. There are a number of ways of doing this, but this one seems to be both the fastest and least complex when it comes to rendering HTML within the text. There are a few problems which are outlined below:

1. Although most HTML is rendered correctly, it is obvious that things such as tables are not going to be shown correctly because they require an ending tag before they can be rendered.
2. Unlike tags, meta characters like &quote; (the " sign), are not looked for. This means that it is possible for only half of the character's value to be written before the display is updated This means that weird text might appear while the parser passes over the character's value. This is reasonably simple to fix by forcing the parser to continue looping until it finds a ";" character after finding a "&" character.
3. The render speed begins to suffer as more and more text becomes visible. I'd assume that the most effective way of solving this would be to divide ones text up into multiple blocks. Then all you'd need is a bit of fancy scripting to start rendering each new block as the previous one finishes.
4. Err, and a few other things that I can't think of right now.

How did I do it? Here's a quick rundown. Firstly we give a <FONT> tag an ID then manipulate the text within this block using it's .innerHTML property. You could however use any other tag that has this property. To begin with, we copy the value of this property to a temporary variable. From then on, to make the text seem to appear, we simply copy more and more from the temporary variable back to the .innerHTML property.