manipulate the content to address the needs of a particular user. P E R C E P T I O N For example, there are a number of guidelines on the presentation of web content to ensure perception of the content by people with various disabilities. These guidelines include providing textual descriptions of images, icons, charts and figures, and providing audio and video files. It also includes identifying headers, lists, tables, and other structured information, so that all of the essential content can be read aloud (or translated into another format) for people who have vision problems or who have difficulties reading. S C R E E N R E A D E R SFor example, the University of Waterloo’s homepage has hidden mark-up that allows the site content to be read aloud in a way that preserves the sequence of information and ignores any decorative content. Take 30 seconds and listen to our university’s homepage as it appears to people who “view” the website using a screen reader. (You’ll need to refer to the course, slide12, to hear the screen reader) Some people who work regularly with screen readers would actually listen to this website at a much faster pace, faster than your brain would be able to process. C A P T C H ASCAPTCHAs pose a particular challenge. CAPTCHAs are distorted images of text that help to distinguish between human users and computer programs. However, users who have vision problems have a particularly difficult time reading the distorted text - even if they enlarge the image - and screen readers are hopeless! Figure 16:PD10 Unit 07 Presentation 2 Slide 11 Figure 17:PD10 Unit 07 Presentation 2 Slide 12 C A P T C H A S A R E D I S T O R T E D I M A G E S O F T E X T T H A T H E L P T O D I S T I N G U I S H B E T W E E N H U M A N U S E R S A N D C O M P U T E R P R O G R A M S .