The border-left-width property sets the width of an element's left border.
The border-left-width Property is used to sets the width of the left-border of an Element.It is mandatory to declare the border-style or the border-left-style property before the border-left-color property
Note: Always declare the border-style or the border-left-style property before the border-left-width property. An element must have borders before you can change the width.
Syntax:
border-left-width: medium|thin|thick|length|initial|inherit;