Search Engine Optimisation and Accessibility
How does a search engine robot compare with a live human being? Unfortunately human beings are frail creatures, subject to all kinds of possible disabilities and injury; blindness, deafness, colour blindness, wrist injury, and so on. The list is endless.
But, if you think about it, a search engine robot or web crawler, software used by the search engines to search out, understand and index websites, has most of the more common human disabilities all contained in one neat package! A web robot:
- cannot see what's on screen
- cannot hear the commentary in a video
- cannot understand the pixels of an image
- cannot associate items on a web page simply by colour
- or by their proximity to each other
- cannot judge importance from text size
- cannot use the keyboard
Simply put, if it's in plain text, and if the correct, semantic HTML elements are used to indicate importance, association, and meaning, then Google et al come, they see, and they go away happy. If the developer does his own thing, and doesn't follow the rules - all the rules - then the search engines miss much, or all, of the sense of the site content.
For instance, if your website's home page consists of just a single large image, or maybe a slide show of several images, with the only text content actually contained in the images themselves (still a very common practice practice in spite of all industry advice to the contrary), then Google will arrive and be mystified. A search engine crawler cannot understand the pixels of an image.
If you include a video on your site, without the associated text transcription that Accessibility standards require, then, so far as the search engines are concerned, there might as well be no video there. Search engine robots don't sit for hours playing videos!
And the list goes on.
Markup Methods for Accessibility
In the world of web accessibility, all the common human disabilities are met by various forms of assistive technology (usually shortened to AT) to enable disabled people to understand and operate standards-compliant websites. Screen readers for the blind are the best known example. The accessibility standards of the Web Content Accessibility Guidlines 2.0 (WCAG) lay down rules for how websites should interface with AT so that the devices can read and understand the markup and act accordingly.
For instance, the WCAG specifies that the web developer must provide alternative text describing every important image. An AT device such as a screen reader can then read aloud to a blind person so they know what is in the image. Another rule instructs the developer never to do headings by simply increasing font size in the CSS, but to use the correct h1 to h6 HTML elements instead, so AT devices know there is a heading there also. Methods like this are how we pass important information to assistive devices. They work equally well for unintelligent web crawler technology.
A technique that is very important to SEO is always to put meaningful text in links, rather than such phrases as "click here". The search engines then compare these link texts to the content found at the other end and, if they match well, they regard them as a "relevant" links. That enhances the SEO scoring for the sites. Accessibility, however, has long made this a required technique for all links.
The Spin-off For SEO
It is a fortunate spin-off of all this that search engine robots can also see everything that is done for assistive technology, and make better sense of a web page as a result. If, for instance, the developer correctly uses h1 to h6 elements to show headings and which level of importance they are, then the search engine robots can also see those heading elements and recognise the structure of the page. Google pays very careful attention to how the web world implements accessibility (that's to say, how they actually do it rather than what the standards say - Google robots are not so interested in the standards per se).
So the best kind of search engine optimisation (SEO), if you want your website to do well in the search engines, is to follow the guidelines for making it accessible to disabled people. Far from being (as some IT departments think) a waste of time and effort, Web Accessibility is good for a website's search engine ranking - even though that's not the reason we should do it!