Here are some ways that I think the internet might change if access is predominantly be mobile phone:
1. HTML/CSS may change dramatically - or a new protocol may be developed so that content is more easily adaptible to multiple screen sizes.
At the moment, the movement is called mobileweb.
Goal is write once, display everywhere (http://streamer.rit.edu/chw.ariadne.mobi/presentations/2007_OxfordFutures/goingDual.html)
Perhaps widgets might be a way to do this? (http://streamer.rit.edu/chw.ariadne.mobi/presentations/2007_OxfordFutures/goingDual.html)
2. more social networking applications & “push technologies” will be developed to capitalise on the strengths of phones. For example, twitter takes low number of character entries.
Generation Y, who sees the mobile as a social device first and an information device second, is not using today’s mobile search as much as expected. But Generation Y is using mobile phones to access social networks.”
http://www.readwriteweb.com/archives/why_gen_y_is_going_to_change_the_web.phpAlready, this is being used for on-the-spot, on-demand volunteerism i.e. volunteer at the precise moment you have the time. This shifts the need from the needs of the organisation to the needs of the individual or wants to do the volunteering.
(see video at http://www.knightpulse.org/blog/08/12/08/what-can-we-change-using-mobile-devices)
3. more web applications will be linked to geospatial data (eg. coupons for local stores may get pushed to your phone as you walk past the store or a local historical society may send you a video, audio or web page that tell you something of the history of the local area)