Building mobile web apps already became pretty easy with user-friendly and high quality frameworks
Mobjectify is a free web application which makes it so much simpler by offering an awesome web-based mockup builder.
The application enables us to create pages and add various web elements (like forms, buttons, content areas, footers, etc.) with few clicks.
It also offers multiple themes to choose from or you can create new themes. There is a live preview and results can be exported as a single HTML file anytime.
Mobjectify powers the mobile web pages with jQuery Mobile + its theme engine and only leaves the custom coding to you.