If you're not familiar, Lynx is the most basic web browser, found on Unix and Linux servers. There are no photos, just pure text, links and forms.
You're probably wondering why you would ever think about supporting a browser that's based in a console window. Does anyone actually browse the web from a bash shell?
And actually, a lot of the traffic to your site is viewing things in this HTML-only form. I'm talking about search-engine spiders, bots, and people stuck using text-only devices such as screen readers.
So run through your site with Lynx now and then. You will be able to see at a glance if there is enough hidden or alternate text on the page to be useful to search engines and the blind. You'll also be able to ensure that forms and functionality are available to absolutely everyone, even people browsing under Bash!
Update: I just discovered Seebot, a web app which lets you browse the web the same text-only way Lynx (and bots) do.