HTML5 will enable developers to use cleaner code, we can remove most div tags and replace them with new structural elements.
As websites adopt the new HTML5 elements we will see far greater consistency in terms of the HTML used to code a web page on one site compared to another. This will make it far easier for web designers and web developers to immediately grasp how a web page is structured even if they are brand new to it.
As the elements used to code a web page are standardized, using the new HTML5 elements, the semantic value of every web page will increase. As it will be easy to see which parts of the page are headers, nav, footers, aside, etc. and most importantly know what their meaning and purpose is in a machine readable format.
With HTML5 it should be possible for assistive technologies to expand on the features they can offer their users as they can immediately build up a more detailed understanding of the structure of a page by looking at the HTML5 elements it contains.
The new HTML5 geolocation APIs make location, whether generated via GPS or other methods, directly available to any HTML5-compatible browser-based application. A good example is the Google Latitude for the iPhone. This is a pure Web App not a platform-dependent iPhone application.
HTML5 provides a new SQL-based database API that can be used for storing data locally, that is client side. You get fully defined and structured database storage. This allows a developer to save structured data client-side using a real SQL database. It is not a permanent database, but enables you to store structured data, temporarily. The data can be accessed to support the web application and it can even be accessed when the client is disconnected for a short period of time. This database can be used to store e-mails or shopping cart items for an online shopping site.
Offline Application Cache
An offline application HTTP cache that can be used to make sure applications are available even when the user is disconnected from their network. All browsers have a cache but they have been very unreliable for delivering whole pages and applications. Mostly the browser would not cache the page properly and so you would be unable to view the page when you disconnected from the Internet. HTML5 provides a smart solution by allowing a developer can specify the files that the browser should cache while online. So, even if you reload the page from the cache when you are offline, the complete page will still load correctly.
HTML5 offers enhanced forms with improvements to text inputs, search boxes and other fields and provides better controls for validating data, focusing, interaction with other page elements on the page and various other improvements.
Sharper focus on Web application Requirements
HTML5 is aimed at making it easier to build search front-ends, wikis, real-time chat, drag-and-drop tools, discussion boards and many other modern web elements into any site, and have them work more efficiently