Has anyone designed a website where they have used the tab key on the keyboard as a primary method to navigate within the navigation of the website? I am doing a website where the client wants to rely a lot on usage of key "tab" on a keyboard rather than a mouse. Just don't have enough experience with this and was wondering if any of you could share your experience in a similar situation or any resources or online articles on it?
Well, you shouldn't really be asking other designers - you should be asking your users. They might have very different expectations to web-adept IT professionals. That being said, I expect that you'll still get the same answer - 'no'. In usability tests, I can't recall seeing many users rely on keyboard navigation.
More to the point, tab keys have a particular meaning on the web: they change the focus on page elements. Anything that disrupts that paradigm is going to confuse people. Even if your users rely on other tools or services where the Tab key has a particular meaning, that doesn't mean they'll instinctively apply the same assumptions to your website.
Sometimes, people will suggest you can get around that with helptext. That won't work. Users do not read ancillary text on websites - they have other priorities.
Now, if your tab key's meaning doesn't disrupt convention (it just shifts focus on elements and fields in your pages), and if the user can still rely on their mouse, fine. But anything else sounds like a bad idea. If your client still insists, though, then conduct a usability test by all means.