As such, to ensure accessibility an alternative
description needs to be assigned to every image and the screen reader will read
out this alternative, or ALT, description:
<img src="filename.gif" alt="image description goes here"
/>
Like screen readers, search engines can't understand images either and won't
take any meaning from them. Many search engines can now index ALT
text though, so by assigning ALT text search engines will be able to
understand all your images.
2. Text displayed through HTML, not images
Text embedded in images appears pixelated, blurry and often impossible to
read for users utilising screen magnifiers. From an accessibility point of view
this should therefore be avoided.
Search engines equally can't read text embedded in images. Well, you can just
give the image some ALT text, right? Unfortunately, there's strong evidence to
suggest search engines assign less importance to ALT text than
they do to regular text. Why? Spammers. So many webmasters have been stuffing
their ALT tags full of keywords and not using them to describe the image. Search
engines have cottoned on to this form of spamming (as they eventually do every
form of spamming) and have taken appropriate action.
3. Descriptive link text
Accessibility & CSS support packages
Get on-going help with:
Problem HTML
and/or CSS code
Accessibility checking of new or existing pages
The writing of HTML/CSS code
Training or advice on accessibility and/or CSS
Visually impaired web users can scan web pages by tabbing from link
to link and listening to the content of the link text. As such, the
link text in an accessible website must always be descriptive of its
destination.
Search engines place a lot of importance on link text too.
They assume that link text will be descriptive of its destination and as such
examine link text for all links pointing to any page. If all
the links pointing to a page about widgets say click here, search engines
can't gain any information about that page without visiting it. If on the other
hand, all the links say, widgets then search engines can easily guess what
that page is about.
One of the best examples of this in action is for the search term, miserable
failure. So many people have linked to George Bush's bio using this phrase as
the link text, that now when is searched for in Google, George Bush's bio appears top of the
search rankings!
4. Website functions with JavaScript disabled
JavaScript is unsupported by about 5% of web users ,
either because they've turned it off (for example to prevent pop-up adverts) or
because their browser doesn't support it. Many forms of JavaScript aren't
accessible to web users utilising screen readers.
Search engines can't understand JavaScript either and will
be unable to index any JavaScript-driven content. Perhaps more importantly,
they'll also be unable to follow JavaScript-driven links. You may really like
the look of your dropdown menu but search engines won't if they can't access
certain pages on your site because there aren't any regular <a href> links pointing at them.
5. Alternatives to Flash-based content provided
Flash, like JavaScript, isn't accessible to many users, including those using
screen readers. Equally, search engines can't access Flash so be sure to provide
equivalents.
6. Transcripts available for audio
Hearing impaired users obviously require written equivalents for audio
content to be able to access it. Search engines too can't access this medium,
but transcripts provide them with a large amount of text for them to index.
7. Site map provided
Site maps can be a useful tool for visually impaired users as they provide a
straightforward list of links to the main pages on the site, without any of the
fluff in between.
Site maps are also great for search engines as search engines can
instantly index your entire site when they arrive at the site map it.
Next to each link you can also provide a short keyword-rich preview of the page.
All links should, of course, be made through regular HTML and not through JavaScript (see
4. above).
8. Meaningful page title
When we arrive at web pages the first thing that appears, and the first thing
that visually impaired users hear, is the page title. This latter group of web
users don't have the privilege of being able to quickly scan the page to see if
it contains the information they're after, so it's essential that the
page title effectively describes the page content.
If you know anything about search engine optimisation you'll know that the
page title is the most important attribute on the
page. If it adequately describes the content of that page then search engines
will be able to more accurately guess what that page is about.
9. Headings and sub-headings used
Visually impaired web users can scan web pages by tabbing from
heading to heading, in addition to tabbing from link to link (see 3.
above). As such, it's important for accessibility to make sure that headings are
correctly marked up by using <h1>, <h2> etc.
Search engines assume that the text contained in heading tags is more
important than the rest of the document text, as headings describe the content
immediately below them. Search engines assign the most importance to
<h1>, then <h2>, and so on. Make sure you use the heading tags
properly and don't abuse them, as the more text you have contained in heading
tags, for example, the less importance search engines assign to them.
10. CSS used for
layout
Screen readers can more effectively work through the HTML code of CSS-based sites as there's a greater
ratio of content to code. Websites using CSS for layout can also be made
accessible to in-car browsers, WebTV and PDAs. Don't underestimate the
importance of this - in 2008 alone there'll be an estimated 58 million
PDAs sold
worldwide .
Search engines also prefer CSS-based sites and are likely to score
them higher in the search rankings because:
-
The code is cleaner and therefore more accessible to search engines
-
Important content can be placed at the top of the HTML document
-
There is a greater density of content compared to coding
Conclusion
With all this overlap between web accessibility and search engine
optimisation there's no excuses for not implementing basic accessibility on to
your website. It'll give you a higher search engine ranking and therefore more
site visitors.
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