Because using this way works:
col-3 col-md-3
And that way it does not work
col-sm-3 col-md-3
Is the first form correct?
Because using this way works:
col-3 col-md-3
And that way it does not work
col-sm-3 col-md-3
Is the first form correct?
Your answer is simpler than it sounds. You are using the classes of one version of the grid in the other. What I mean is that you are using the Grid classes of Bootstrap 4 in Bootstrap 3. It does not work.
The col-3
class does not exist in Bootstrap 3, so it does not work. You can replace with col-xs-3
I the smallest pro grid measure of BS3
Official documentation of the BS3 grid : link
OfficialBS4griddocumentation: link
So you see that in BS3 there is not only the class col-*
as in BS4 does not have the class col-xs-*
col-3 col-md-3
works only on BS4
col-xs-3 col-md-3
works only on BS3
col-sm-3 col-md-3
works on BS3 and BS4