I'm working on a mobile phone web app and I have several text fields that could benefit from <input type="tel"/>. iPhones will adjust the keyboard for the user, but I'm worried about breaking backwards compatibility. What I'm hoping is that browsers/phone that support this can assist the user and other browser will fall back to a standard text field? Is this an acceptable practice? Does it even work?
Yes, any unsupported type will revert to the 'type=text' format.
I found a good page which lists out all the existing input types. I tried looking at it from different browsers, a bit interesting. Don't know if it will help you or not.
Browsers will fall back to type="text" when they encounter unsupported input type. So I think it's OK to use type="tel".
Short answer: yes. As @el.pescado mentions, browsers fall back to type=text when they don't undertand the type. For more info about the other cool features you get from HTML5 forms, check out A Form of Madness, which is the forms chapter in Dive Into HTML5.
来源：https://stackoverflow.com/questions/2813997/is-it-okay-to-use-input-type-tel-now