Is your blog hosted on WordPress? Watch this video to learn where to put your custom CSS changes and homework assignments.
A Note About Themes Updates & Changes
When putting your CSS style changes in the Appearance > Editor section, please note that those styles will disappear if:
So if you use this method, be sure to save your style changes in another location (ie a blog post draft, a Word Doc, etc.) so that you do not have to re-figure out those style changes.
A Note About Caching
Is a style not appearing right away on your site? It could be an issue with caching. Give yourself 30-60 seconds and then hit refresh again.
Pro tip: If you have a plugin (like WP Super Cache) or a setting that cache's your site, you can either disable your plugin or clear or "flush" your cache to help make the changes appear earlier.