Any effective use of PowerPoint will consider the environment in which the presentation will take place. Indeed, failure to consider the presentation environment can be disastrous. The Internet presents an environment with both limitations and possibilities for using PowerPoint. While it is possible for students simply to download your .ppt files, this method requires download time and makes it necessary for students to have PowerPoint of a PowerPoint viewer installed on their machines. In addition, there is the opportunity for conflicts between different versions of PowerPoint. It is therefore better to convert your presentation to a format that will work as seamlessly as possible on the Internet.
It is possible to convert you PowerPoint to HTML. Problems and limitations result, however, depending upon the Browser that the student is using. The appearance of the presentation - including animations - can vary among Internet Explorer, Netscape, Firefox, etc. Moreover, converting to HTML may not reduce the total file size of a presentation.
The best way to format your presentation for the Internet is to use a product such as Camtasia to convert your file to Flash. Using Camtasia to convert a PowerPoint to Flash has numerous advantages over "raw" PowerPoint or HTML PowerPoint. (Some of these have already been cited.)