I use the Bootstrap framework to layout my websites. Currently I use V4 which is still in the development stage. Although not yet recommended for production sites I decided to use it for mine so that I can learn as they progress through the Alpha a Beta stages. This involves looking and incorporating changes as they add them.
Currently Alpha 6 as recently been released. This is large change as they now use Flexbox as the default. I decided earlier on to use the flex option as my basis even though it restricted me to newer browsers. This has resulted in the implementation of Alpha 6 being somewhat easier. But each page still has to be checked and tested so my live site will be updated in the next couple of weeks.