The WWW is a client/server hypertext information system. This means that the information resides on a remote machine (server) and is accessed by a program (client) that is run on the user's machine. The client program is responsible for retrieving the information from the server and ``displaying'' it on the user's workstation.
Here is a list of popular WWW clients. Each client is accompanied by a brief one-line description covering its current level of accessibility using speech interfaces.
As can be seen from the above, the WWW is not entirely closed to persons with visual impairments. At the same time, the level of access clearly leaves much to be desired. I myself use the Emacs W3 browser, and except for being unable to see the pictures on the WWW, this browser gives me complete access to any information that is archived without assuming a pure visual presentation. We will address the question of such archival in greater detail in section 3.
Most of todays WWW clients have been designed with a visual interface in mind. Though a fair degree of access can be provided via generalized screen-reading programs, we point out that in the general case this approach can break down. This is especially true when the information being displayed is structurally rich; e.g., technical documents containing mathematics, tables etcTeX. This is because in the case of structurally rich information that has been displayed visually, a screen-reading program that merely speaks the contents of the visual display fails to convey the structural information that is essential for the user to understand the content. A typical example of this is provided by general screen-reading programs attempting to speak a displayed table.
The above shortcoming is not readily apparent on the WWW today, since most of the information available is not structurally very rich. As the WWW matures and begins to be used for professional publication services, the above shortcoming is likely to become more readily apparent.