A couple of comments:
You have essentially replicated the first step I took that led to the creation of Categories Dressing five years ago, adding the <hr> after a category link (or all of them, in your case). However, you have used <hr id="catBoxDivider" /> which gives dozens of elements with the same id.
An id is supposed to be unique on a page, so you should change your code to <hr class="catBoxDivider" />. You now have doubled dividers at the bottom of the category list, so you should turn off the original one in Configuration > Layout Settings > Categories - Separator between Links.
On a completely different topic, I notice you have pasted a complete HTML document inside your category description. This extra doctype, head and body code will cause major validation errors on your page, and each browser will have to try to correct the output, possibly with different results in different browsers.
You need to strip your content of all these container tags and put the style rules in your stylesheet instead of in the middle of the page code.