The HTML for creating a Horizontal Line is

<HR>

To make the Horizontal Line thicker add a size to it like this

<HR SIZE="6">

To give the Horizontal Line colour use this HTML (experiment with colours of your choice)

<HR COLOR="RED">

<HR SIZE="5" COLOR="GOLD">

To change the length of the horizontal line try this HTML

<HR WIDTH="50%">

<HR SIZE="7" COLOR="BLUE" WIDTH="50%">

You can even align your horizontal line to the left or right like this

<HR SIZE="7" COLOR="BLUE" WIDTH="50%" ALIGN="LEFT">

<HR SIZE="7" COLOR="BLUE" WIDTH="50%" ALIGN="RIGHT">

Note that there is no closing tag for <HR>.