P E R C E P T I O N For example there are a number of guidelines on the

P e r c e p t i o n for example there are a number of

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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 S For 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, slide 12, 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 A S CAPTCHAs 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 .
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14 © University of Waterloo and others If a website wants to be accessible and include CAPTCHAs, it needs to include alternate forms of CAPTCHAs, such as audio CAPTCHAs. Implementing audio CAPTCHAs is tricky, because you don’t want the audio commands for controlling the playback of the CAPTCHA to interfere with the audio CAPTCHA itself. Try your hand at passing an audio captcha. (You’ll need to refer to the course, slide 13, to hear the audio CAPTCHA) O P E R A B L E Web accessibility is not just about how to present information to users. Many web pages are interactive. Regardless of their disabilities, users need to be able to provide input commands, select menu options, and enter text. Many well-recognized keyboard shortcuts exist that substitute for mouse commands and most web browsers support these. It also helps if the web designer provides multiple ways of navigating through the website content. Providing navigation options allows users to reach the information they are looking for more quickly and with fewer commands.
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