So, you've found your theme has a code for the hr or you've copied and pasted the css code in this tutorial into the stylesheet. Now you need to customize it to however you want it to appear on your pages or posts.

First let's look at the top and bottom margins, this is the space above and below your horizontal line:

The above example is 1em (12pt) space above and below, you can reduce or increase this space by changing the figures ringed in red:

For example 0.5em would reduce it by half (6pt), 1.5em (18pt) will increase the space by 6pt.

As mentioned earlier, by default your horizontal line will be the same width as your body text, so we'll leave the left and right margins for later and show next how you can really make your horizontal rule stand out.