The border-width property in CSS is used to set the border width of all the four sides of an element. The border-width property is the combination of four property
The border-width property sets the width of an element's four borders. This property can have from one to four values.
Examples:
border-width: thin medium thick 10px;
top border is thin
right border is medium
bottom border is thick
left border is 10px
border-width: thin medium thick;
top border is thin
right and left borders are medium
bottom border is thick
border-width: thin medium;
top and bottom borders are thin
right and left borders are medium
border-width: thin;
all four borders are thin
Note: Always declare the border-style property before the border-width
property. An element must have borders before you can set the width.