The internet is an important and mandatory part of modern life, including the 285 people million worldwide who have some form of visual impairment (1.4 billion web users worldwide have accessible needs). However, those with visual impairments are often unable to use much of the internet as many sites demand that lack features necessary for low or no vision users. The lack of sight isn’t the only issue as approximately 8% of the male population experiences one of the three forms of color blindness. Visually impaired users comprise of a large segment of the population, usually around 10%. It’s important to provide an accessible site so that you can reach all your customers without inadvertently adding challenges for some. Additionally, there are laws that US government websites as well as websites at some companies or sectors must adhere to defined by http://www.section508.gov/. Before jumping into the technical aspects of accessibility, let’s look at how visually impaired users “see” your web pages.
How the Visually Impaired Use the Internet
The internet is largely visual, and that can exclude people who have visual impairments from accessing its contents. Low vision users often require the use of assistive technology, usually in the form of a screen reader. While most people need to increase the browser’s font size frequently, those with severe impairments must use a screen reader such as JAWS, NVDA, Window Eyes, or one of the many others. If you’ve never used a screen reader, you can watch this video about how a blind student uses the internet that should give you a sense of what it’s like. Screen readers are quite robust in their capabilities, but they do have limitations, and cannot completely substitute for the visual experience, especially in a graphic laden site. That’s because screen readers cannot read videos or image data, only textual data and DOM elements. Additionally, low vision and blind users rely heavily on using the keyboard, since a mouse demands high fidelity eyes as well as hands to work. That means non-mousers use Tab/Shift keyboard combination in a Windows system to move between heading level tags, named anchors, and form elements, sometimes while waiting for the reader to catch up. This is the opposite of a sighted person who’s eyes can quickly scan away from redundant menus or ads to get to the good content.
Others may have a contrast sensitivity rather than, or in combination with, low or no vision. When one has a visual issue that affects contrast, the eye has reduced ability to distinguish between similar shades and levels of brightness. That makes the experience of color different from that of what we classify as normal vision. In fact, the popular social networking site Facebook uses color code #3b5998 (dark blue), because its founder Mark Zuckerberg is colorblind. Eye diseases such as Retinitis Pigmentosa, Retinopathy, Cataracts, and Glaucoma all lead to sharp decreases in contrast and/or color sensitivity. The colors actually look different to folks with contrast sensitivities. What you see as red might look brownish or even gray to someone else. This article at MSDN reveals how users with varying colorblindness and contrast sensitivities see web pages.
Accessible Content and Design
When building accessible web pages, we can do many things that will enable their usage for people with assistive technology. The first and easiest step to take in creating visually accessible web pages is to increase the default font size! Most of the citizens of the world do not have 20/20 vision, so increasing the font size is a tremendous gain with only a single line of code to change in the site’s default CSS file. When crafting hyperlinks be sure to set the link text (i.e., the text between the anchor tags) to something descriptive that matches the link target. Avoid generic text such as the words “Click here”, and be sure to include a complete description of what the user can expect on the other side of the link. Applying the name attribute to anchor tags means users can use the keyboard to skip through to that hyperlink.
Two colors that have low contrast might be fine to someone with normal vision, but it is likely harder to distinguish between the colors, letters, and symbols for someone who is colorblind. Quite possibly the most important design concept for accessibility is to keep the site clean of clutter, and navigable with alternative methods of input than a mouse. You can ensure your color schemes and contrast work well by visiting these sites: http://webaim.org/resources/contrastchecker/ and http://www.checkmycolours.com.
Screen readers must read everything on the page they can access (usually DOM and text), and that includes headers and footers that show on every page in the website. It can take several minutes to plow through a menu that a sighted user can scan in just one second. To remedy this, we use Skip Links. Skip links are HTML anchros that allow the speech software or braille user to bypass redundant information, such as navigational menus. Speech and braille users generally read the page from top to bottom, and consequently are subjected to repeated information before reaching the heart of the page. All you need are two lines of code. Just put an anchor before the repeated HTML (usually a menu), or right at the beginning of the page, like this:
Then place a named anchor at the beginning of the unique content, where the reader’s eyes would normally skip to:
Then you have a skip link. This tag can exist anywhere in the page that you think the screen reader should land, so it can continue reading from there. Adding something as simple as skip links in your source enables the machine reader to save a significant amount of time on behalf of the user. Check out the skip links at WebAIM. They work perfectly.
Accessible HTML Layout and Elements
You can craft accessible HTML with little to no extra effort than you normally use in your daily development tasks. Simple things like using header tags, <h1> through <h6>, make the page navigable via keyboard, as low vision users may have difficulty seeing where to mouse. Avoid using <div>, <span>, or <p> tags with larger fonts, as they don’t allow for keyboard navigation or work well with assistive technologies. Besides, <h1>-<h6> are meant for headings. When displaying media, each <img> element must have clear and succinct alt attribute value, as this is the only way assistive technology such as screen readers and braille machines can convey what is inside the image. This is an easy coding task. When laying out sections of pages with HTML <tables>, be sure to include the <th> elements for navigation and assistive technology, rather than using <td> tags for column headings.
The Web Accessibility Initiative established WAI-ARIA, the Accessible Rich Internet Applications Suite, as a way to make Web content and sites more accessible to people with disabilities of any sort that makes computing unnecessarily difficult. WAI-ARIA published a set of standard attributes so that HTML can integrate with assistive technologies.
Accessible HTML Forms
Submit and reset buttons as well as the <button> element automatically work with assistive technology. You must make some minor modifications to other form elements though. Using the <label> element is a very effective way to enable screen readers and braille machines to present the text and meaning of any HTML input tag. When building HTML forms in general, be consistent with the placement of labels and input fields, and be sure to explicitly state required fields and validation. While it is a common practice to indicate which items are required fields with a non descript red asterisk or icon, it is not very accessible. Adding the word “Required” or a precise description of the validation message to the label makes validation rules clear to readers and devices. Label all input elements of the form. Below is a sample of the proper way to label for accessibility:
Notice that the <label>’s for attribute matches the <input>’s id attribute. Without this connection, visual assistants cannot determine which labels belong to which element. When working with dropdowns, label the entire dropdown as well as each individual item in the dropdown by placing text between the <option> elements..
Checkboxes only need that you use the <label> element, and they’ll work with readers. The American Association of the Blind recommends avoiding Radio buttons, stating that many of the assistive programs out there do not support them well. Since radio buttons often represent simple binary data or yes/no answers, a checkbox should work fine as an alternative. You can move to a drop-down for three or more items.
In addition to open standard HTML, the WAI-ARIA standards provide ARIA tags that you can use to enhance assistive technologies, especially in HTML forms. You can apply the aria-label attribute to elements that have no text, such as an image or a submit button. Form elements that you require the user to fill in should have the aria-required attribute set to “true”. Our previous example that creates a text box to contain a full name can be expanded like this:
The American Association of the Blind has many resources for creating visually accessible web sites. Hide your mouse away while testing web pages to force yourself to be a keyboard user, and test for harmony with assistive technology. You can do so by trying out a few of these 10 free screen readers, or the Web Anywhere browser based screen reader that requires no software installation. Before you publish your web site check out the Web Accessibility Evaluation Tool (WAVE). This tool lets you plug in a URL and it will show that same page with annotations specifying its level of accessibility compliance. Finally, Microsoft has released an Accessibility Center where you can learn about various development techniques and tools to help you reach all of your customers.