Whether you're building a house or a website you'll need to follow certain standards - codes. As someone who transitioned from the building trade to web design I've been amused by similarities in these two seemingly disparate professions. Much of the terminology is the same. I've already mentioned build and code.
Analogies are useful but they're eventually dead ends. Rarely did I walk onto a construction site and say "shall we start with the roof or the foundation today?." I say rarely, because remodeling is another beast. Much like retrofitting an inaccessible website.
In the young trade of website construction some of these fundamentals are still being hammered out. Content First anyone?
I started playing with html in 1994 and by '96 I was volunteering to build websites for non-profits where accessibility was essential. So thinking about accessibility has been with me from the start. I wysiwyg'd my way through the design and then built a parallel text only site. Good Lord man!
Meanwhile back at the Web Standards Project a battle was being fought and won. The giant corporations, Microsoft and Netscape, were defeated ... by the people.
A couple of caveats. In the first paragraph I mentioned building a house and standards. Currently the laws regarding meeting accessibility standards apply mainly to government buildings and government websites. That's changing. A couple of years ago Target was forced to make their website accessible. Huge uproar. Then they fixed their site and they're doing fine.
Why would you want to exclude customers. And why would you want to exclude visitors from your home. Don't know any wheelchair users? Stop me if you heard this one: any one of us - me, you, your family members could become disabled in an instant. Add the cost of the construction retrofit to your medical bills.
And finally, in the "Boy do we still have a ton of work to do" department. The following embedded video has no captions or audio description.