If you've used either Apple's Interface Builder or Microsoft's Blend to build UI, then having to do it by hand in HTML seems like a big step backwards. But there is help and it is free. The Intel Open Source Technology Center has released its Rapid Interface Builder (RIB) tool. It runs only in Google Chrome, but it will save you huge amounts of time laying out your UI.
RIB supports both jQuery Mobile and Tizen (a new mobile still in development) widgets. It allows create your UI in the browser then download the source code to your PC. Later I will do a more in-depth walk-through of this amazing tool.