Changing the color of visited links can help your visitors alot. This is especially useful in situations where you have a page with a lot of links. You can change the color to any color you want.
This tutorials will teach you how to put your weebly blog posts into columns. Weebly usually puts their posts in a list. If you don't like it this tutorial is perfect for you.
A captcha can help keep unwanted spam and bots away from you site. This tutorials shows how to add a very simple but affective captcha checkbox.
A 404 page is a page where the website directs to when a url is broken or when the url doesn't exist. Weebly has their own 404 page but if you don't like it, you can follow your tutorial to make your own.