We like to tell ourselves that the mobile web has arrived, but the reality is that it may not be as close as we might like to think.

Desktop applications and web sites have since the 1980�s been designed assuming multiple windows. If you want to get information from another application, just open it. Browsers can have multiple windows open. This is particularly important in our current world of online applications: I can have my email window open, my business networking site open to research somebody in my email, and my calendar open - all in separate windows. Mobile phones do not support this cross-site fertilization. Instead, only one �window� can be viewed at a time.
For �one web� can become a reality, browsers must become adept at handling multiple tasks. This, by itself, is inadequate. High-end phones (variously called �smart phones� and �PDA phones�, usually with an operating system like Symbian, Windows, or Palm) have rudimentary multi-tasking - but on an application level. Multiple browser tasks must become easy; switching between pages must become easy; split-window viewing must become possible…. Source: emergic.org