tongo
So I had a routine that normalized the address, as best I could anyway, didn't help that it was all just one varchar field. Then implimented Levenshtein Distance, messed with the weighting a bit to fit our particular data and away it went. Saved a bunch of headaches. It wasn't perfect, but it was better than hand matching a couple thousand accounts.
First, can you navigate your entire site without using a mouse (including any widgets, forms, embeded stuff)? You should also have a "Skip to main content" button that is the first element you hit when you tab into your page.
Next, download the NVDA screen reader, which is free, turn off your monitor (or close your eyes), and navigate your site using it. I recommend using FireFox for this.
Finally, use a color contrast analyzer plugin for your browser to ensure you have enough contrast between all of you elements.
From there, you can review the WCAG 2.0 spec to get into the fine details. If you have the budget, hire a consultant/contractor. What I described above doesn't make your site pleasent to use for a disable person, just usable.
It's also always place this field after the Submit button with the idea that a user with a screen reader would never make it that far. Bots still see it and add it to the post request since I don't think they care about the order of the form fields.