How to center elements?

Question

css

How to put the form in the center on the site , what columns should be specified in HTML? I don't understand how these col-md-3 and so on work.
Form: https://tppr.me/l7LgN

Answer 1

col-md-3 is a class that, in the standard bootstrap grid, gives a box width of 25%. You can specify the offset in col-md-offset-3 - this will indent 25% from the edge of the screen, you will get a block in the middle, but you also need to set col-sm-offset-0 so that there is no indent on small devices .
There is another way with display: table. Learn more about all methods here.