HTML5 is built to be versatile enough so that third party plug-ins would not be required. HTML5 nativly supports many features that were only available via plug-ins in all prior versions of HTML. The main reason behind this drastic shift was in lack of plug-in support after installation, ability to disable plug-ins, hence rendering problems. Plug-ins were prone to hacker’s attacks and were difficult integration with HTML page they were embedded into. Plug-in install was another big issue. Many anti-virus programs plainly blocked plug-ins from installs. 

HTML5 provides native APIs for elements of the page to talk to each other. JavaScript can now easily interact with CSS code. Elements of one program can now interact with another without artificial boundaries mandated by plug-ins.