The mobile web is emerging as something powerful and disruptive. Everything old is new again on a smaller screen with a sketchy battery and the likelihood of lost connectivity. It's tricky to know how to get started.
This article will provide you a high level view of the available tools, frameworks and libraries to help you get started with more confidence. The good news is that the mobile web isn't really much different from the regular web tools, libraries and frameworks. The bad news is that the performance characteristics and testing requirements are wholly different.
DOM frameworks
Building anything for the Mobile app development web with any interactivity requires the language of the web, JavaScript, to work with the DOM (Document Object Model). Working with the DOM from JavaScript has been historically tricky. In the past, we needed DOM frameworks to paint over the differences between browser implementations. Thankfully, things are less fragmented today between implementations. In fact, modern browsers today are surprisingly consistent and powerful. This is especially true with mobile web browsers.
It's good to know when you need a technology, but it's even better to know when you don't require a dependency because the only thing faster than code you didn't write is code you didn't have to run in the first place.
If you're targeting recent versions of mobile app browsers, and your app is fairly trivial, then authoring your code straight to the DOM is the way to go. If you find yourself adding lots of boilerplate for selecting/adding/removing DOM elements, network communication and animation, then it's the time to have a look at DOM frameworks.
CSS frameworks
Authoring and testing CSS for the multitude of today's browsers across different devices is hard work. Developers can save time by using open libraries to share that testing, and bug fixes, and get a leg up on time to something that's demonstrable.
As with JS libraries and frameworks, these solutions for CSS can come with a size penalty.