HTML5 APIs HTML5 introduces lots of new and exciting things for web authors, among these are new APIs. Here are some of them.
Application Cache API An API to interact with the application cache, which is a set of cached resources.
You can do window.applicationCache to get the ApplicationCache object that applies to the active document of that window. More on application caches here.
DataTransfer API The DataTransfer objects are used to expose the drag data store that underlies a drag-and-drop operation. More on drag and drop here.
Command API A command is the abstraction behind menu items, buttons, and links. They are defined to have facets (label, hint, icon, etc.) and are exposed on elements using this API.
Constraint Validation API As of this writing, there is no proper definition to this. But we can assume it'll extend our client-side validation tool arsenal.
History API The History objects provide a representation of the pages in the session history of browsing contexts.
For example, you can go back (window.history.back()) and forward (window.history.forward()). More on session history here.
If you use user authentication, make sure you check for it on the request page! Check for SQL Injections Check for JavaScript Injections Keep the Business Logic on the server! Don't assume every request is real! Check the data with validation! Look at the request’s header information and make sure it is correct