HTML5 has many new syntactical features, which include the <video>, <audio>, and <canvas> elements, as well as the integration of SVG content. Due to these new elements, it will be very easy to integrate multimedia and graphical content to web without using flash and third party plugins. There are also another new elements like <section>, <article>, <header> and <nav> which enrich the semantic value of the document.
Cleaner markup / Improved Code
HTML 5 will enable web designers to use cleaner, neater code; we can remove most div tags and replace them with semantic HTML 5 elements.
As websites adopt the new HTML5 elements we will see more consistency in terms of the HTML used to code a web page on one site compared to another. This will make it easier for designers and developers to immediately understand how a web page is structured.
HTML5 makes creating accessible sites easier for two main reasons: semantics and ARIA. The new (some currently available) HTML headings like <header>, <footer>, <nav>, <section>, <aside>, etc. allow screen readers to easily access content. Before, your screen readers had no way to determine what a given <div> was even if you assigned it an ID or Class. With new semantic tags screen readers can better examine the HTML document and create a better experience for those who use them.
Rich Media Elements Support
Forget about Flash Player and other third party media players, getting a video to play earlier has always been a nightmare with thetags and the scores of parameters that go with it for the plugin. HTML 5 has inbuilt capability to play video and audio, so we can say goodbye to the messy plugin tags. An example is illustrated below:
Offline Application cache
HTML 5 offers the developer the ability to specify what the browser should cache, what this means that HTML 5 offers an offline application cache facility which would load the page the user has visited even if the user is temporarily offline. This feature helps the files load much faster and reduced load on server.
Cookies have been used to track unique user data for years, but they have serious limitations. The biggest flaw is that all of your cookie data is added to every HTTP request header, which ends up having a measurable impact on response time. HTML 5 solves this issue with the help of a concept called Local Storage. It’s better than cookies because it allows for storage across multiple windows, it has better security and performance and data will persist even after the browser is closed. Since it is essentially a client side data base you don’t have to worry about the user deleting cookies and it seems to have been adopted by all the popular browsers.
Mobile and Geo-Location
Mobile devices are taking over the world. The adoption of mobile devices continues to grow very rapidly and this means that more and more users will be using their mobile browsers to view your web site or application. With Adobe announcing the death of mobile Flash, HTML5 is the most mobile ready tool for developing mobile sites and apps. Mobile browsers have fully adopted HTML5 so creating mobile ready projects is as easy as designing and constructing for their smaller touch screen displays. The new HTML5 geo-location APIs make location, whether generated via GPS or other methods, directly available to any HTML5-compatible browser-based application.