HTML5 brought with it a huge set of capabilities that enable developers to build sophisticated web applications in conjunction with JavaScript. But it is the native capabilities of HTML5 that are worth investing time and energy.
For instance, HTML5 introduced better semantics that allow you to define categorical areas of a webpage such as the header, footer, navigation and more. For such areas of the page, HTML5 provides semantic tags that ultimately make your code readable and maintainable. This also has far reaching effects in making your website accessible to people with impaired abilities.
HTML5 also introduced specialized form elements that are of particular interest to web application developers. For instance, the meter and progress elements can be used to display a value within a range and the progress from 0 to a given value respectively. Likewise, input elements now benefit from the email, url, date, datetime, month, week, time, number, range, tel and other specialized types that help implement dynamic form elements which were earlier possible only using JavaScript. For instance, the date input type produces a ready to use datepicker widget, something that used to take a fair amount of HTML, CSS and JavaScript in the past to create and use.
Besides these, HTML5 also enables developers to incorporate, audio/video capabilities natively, without the need for specialized plugins/software. You also get to work with vector graphics using SVG which enables the use of dynamically scalable and lossless graphics and animation that is lightweight and easy to use. HTML5 also includes a huge array of specialized interfaces such as Canvas for creating and animating vector graphics, storage for utilizing the browser’s storage capabilities in web applications using JavaScript, an interface for obtaining network related information so as to control or govern behaviour of the web application in case of slow network or loss of network, an interface to play with the vibration motor present in mobile devices which is useful for enhancing user experience and accessibility, an interface that provides the battery status of the device your page is being viewed on, and several other key features that enable the creation of truly remarkable and beautiful looking web applications that are fast replacing desktop editions of software.
And complementing HTML5 is CSS3 which offers innovative ways to create amazing visual elements. For instance, you can natively create animations and behaviour driven transition effects easily with just CSS3. These were previously only possible using complicated JavaScript. Likewise, you also get a host of CSS selectors that allow you to target HTML elements using unique features such as selecting the first line in a paragraph or selecting all odd or even elements or selecting elements that aren’t empty and so on. You also get to create rich gradients, patterns, tooltips and implement rich typography using web fonts that have truly revolutionized the look and feel of websites and web applications. And last but not the least, CSS3 also facilitates the creation of responsive websites which adapt their layout as per the screen resolution being viewed upon. This has direct impact on the user experience and accessibility. You also get a ton of super cool features like 3D transformation, the ability to use multiple and layered backgrounds and column-based layouts among other things.