HTML5 (No space between "HTML" and "5")is a markup language used for structuring and presenting content on the World Wide Web. It is the fifth and current version of the HTML standard.
It was published in 28 October 2014, W3C also published an HTML 5.1 Candidate Recommendation on 21 June 2016. The World Wide Web Consortium (W3C) to improve the language with support for the latest multimedia,..
The CSS was started to develop around 1998. And till 2009, it was under development. The first working draft of CSS3 came in 19-01-2001. but it was initially declared early in the June 1999. The main difference between css2 and css3 is Media Queries, Namespaces, Selectors Level 3, Color.
Bootstrap includes a responsive, mobile first fluid grid system that appropriately scales up to 12 columns as the device or viewport size increases. It includes predefined classes for easy layout options, as well as powerful mixins for generating more semantic layouts.
Bootstrap 4 alpha 1 was released on 19th August 2015. Since then there have been many alpha releases. And finally after that on 10th August 2017, Bootstrap released the first beta for the version 4 of Bootstrap. Bootstrap 4 Beta 2 was released on October 19th, 2017. The bootstrap is world's most popular frontend framework for building or developing responsive websites, mobile-first sites and web applications.