Why re-invent the Wheel?

UI Frameworks:

Making a website in the 1990’s was probably a pretty lucritive job, fewer people had access to computers compared to now, and even fewer had the required skills to make functional yet aesthetically pleasing sites. Over the the years, the cost of computation dropped while compute power surged, and its became easier making pretty decent websites. With all that, HTML and CSS, being the backbones of any website, have evolved very slowly, to a point where we can not make nice enough websites at the speed we need. This brought led to a wave of new technologies that branched to either focus on front end (UI) or backend workings of a web applications

UI Frameworks are scripting languages meant to simplify the creation of pretty websites. They take care of all the css for you and let you focus only on the skeleton of the wbsite. some of the most common UI frameworks include Semantic UI and Twittter Bootstrap. uisng semantic UI has reduced my front end development time from about 4-5 hours for a responsive site to about 1-2 hours. Although you have to also learn the class commands, its nothing nearly as painful as learning pure css and html tags from scratch due to the english like commands you use to describe what you want.

 <div class="ui inverted blue borderless stackable topmenu">
 </div>

For example will create a blue background menu at the top of your site with no visible borders and the menu items stack ontop of each other when viewed of a smaller width device. How much more specific can you get in plain english speacking to a machine?!

Not only does it have everything you need, but also any configuration you might want to get done with minimal css. Replicating a site pixel for pixel using semantic ui is soo trivial, its unbelievable.
The question at the end of the day is not if, but which UI framework you will use?