Should I have a text size widget for accessibility on a charity website?

I'm a developer at a small web agency that works primarily with charities. We tend to put a simple textsize widget on every site (eg. top right on www.embraceme.org). I find myself wondering if that's necessary: if someone has difficulty seeing, then there's a number of tools at the OS/browser level to help them out. If each website reinvents the wheel then that's a new tool the user has to keep relearning (not to mention extra and unnecessary complication on the site). We don't have an accessibility/usability specialist, so would love to hear people's views on this.

Answer

Providing such font size options within individual websites isn't as important nowadays than it used to be (for instance when IE6 was a more common browser as it didn't really have a suitable font resizing option) but that doesn't mean it no longer has its place; it is particularly useful if the target audience for the website is more focused to users with disabilities - such as for the London 2012 Paralympics.

However your main priority with font sizes is to ensure you put your site together using correct modern HTML standards rather than focusing on minor 'widgets' here and there.

The main accessibility requirement around text resizing is that:

WCAG 1.4.4 Resize text: Except for captions and images of text, text can be resized without assistive technology up to 200 percent without loss of content or functionality. (Level AA)

This can be achieved in a variety of ways, all using good HTML standards. For example, use standard readable fonts, don't set your default font size too small, keep your fonts in ems instead of px so that they resize correctly when the user adjusts the font size via the standard browser controls, and keep your layout adaptive / fluid so the content doesn't expand out of the screen / containers when the font size is increased.

There are some good suggestions about how to keep your text accessible at the w3c site - Understanding SC 1.4.4 Resizing Text as well as at webaim.org

Check your target audience for your project. If the users are more likely to benefit from the in-page font resizing due to minor visual disabilities or those that suffer from dyslexia, or (and I hope this isn't the case anymore) if they're locked into using IE6 then yes, it's probably going to be useful to provide that option, but for current web design it's more important to get your code in shape and use good HTML and you can let the users take control of how they want to experience the web.