Some interesting points from usability expert Jakob Nielson that suggests one site cannot fit all.
Summary: Good mobile user experience requires a different design than what’s needed to satisfy desktop users. Two designs, two sites, and cross-linking to make it all work.
Build a separate mobile-optimized site (or mobile site) if you can afford it. When people access sites using mobile devices, their measured usability is much higher for mobile sites than for full sites.
A mobile app might be even better — at least for now.
If mobile users arrive at your full site’s URL, auto-redirect them to your mobile site. Sadly, many search engines still don’t rank mobile sites high enough for mobile users, so people are often (mis)guided to full sites instead of the mobile ones, which offer a vastly superior user experience.
Offer a clear link from your full site to your mobile site for users who end up at the full site despite the redirect.
Offer a clear link from your mobile site to your full site for those (few) users who need special features that are found only on the full site.