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Blindness
Blind people don't need a display for using the internet. A mouse is also unnecessary because blind people cannot see the mouse pointer.
The content of an internet page can be read by a screenreader. This is a voice output that read texts and descriptions of images loudly to the user.
A lot of blind users read the content with the help of an output device that is placed in front of the keyboard. It converts the text into Braille: 8 pins represent each character and each number as a pattern. The blind reader feels for the character with their fingertips. The Braille output device is more accurate than a voice output. The user can check the spelling and it is easier to understand the spelling of borrowed words. A Braille output device can show 40 or 80 characters.
Only if information is available as text and not only as image files is it possible for blind users to use internet pages easily. Images without alternative text description do not exist for them. For example blind people cannot navigate through internet pages if the navigation only consists of images without a description. In this case the user can only guess which item leads to the desired content.
Users without visual impairment will normally not notice if an internet page consists of frames or not. With the eyes they can discern the areas which are framed by scroll bars. On framed internet pages blind users can request a list with information on the frames. So it is possible to jump directly to the desired content. If frames are not named clearly it is difficult for blind internet users to get their bearings. They can only guess if the description ´fr01´ refers to the navigation frame. Pages with too many frames are also a problem.
Blind people need much more time to capture contents than other internet users. People who can see are able to skip sections that are not interesting for them. Heading lists make it possible for blind users to find contents much faster. The screenreader software can show all headings of a page in a separate window. By choosing a heading the user can jump directly to the corresponding content. So it is possible to skip less interesting sections. The screenreader is only able to show the headings if they are logically marked in the HTML source code. Headings that are only formatted bold are not considered.
Links can also be shown in a separate window. But the link lists only make sense if the links are described clearly. If only "more" or "forward" appears, the users do not know which contents are associated with.
The screenreader software reads all texts consecutively in the order in which they are filed in the HTML code. In tables the content of cells will be read from left to right and from top to bottom. If the text is not logically ordered within a table, the reading order can be confused. Even if the content is ordered correctly for sighted users it could be read in the wrong order by screenreaders.