m-t-3 or m-b-3 It should be mt-3 and mb-3

Hi,

It should be mt-3 or mb-3. The pattern is: {property}{sides}-{size}.

Where property is:

• m (for classes that set margin)
• p (for classes that set padding)

Where sides:

• t (for classes that set margin-top or padding-top)
• b (for classes that set margin-bottom or padding-bottom)
• l (for classes that set margin-left or padding-left)
• r (for classes that set margin-right or padding-right)
• x (for classes that set both *-left and *-right)
• y (for classes that set both *-top and *-bottom)
• a (for classes that set a margin or padding on all 4 sides of the element)

Where size is one of:

• 0 for classes that eliminate the margin or padding by setting it to 0
• 1 (by default) for classes that set the margin or padding to $spacer-x or $spacer-y
• 2 (by default) for classes that set the margin or padding to $spacer-x * 1.5 or $spacer-y * 1.5
• 3 (by default) for classes that set the margin or padding to $spacer-x * 3 or $spacer-y * 3

You can find more information utilities/spacing section in the bootstrap4 documentation

Bootstrap4 still in development, so there are things that might change.

I hope it helps. Have a nice day