An important 21st century literacy is that of coding, or programming. Whether or not we become professionals at it, we all need to understand the concepts of coding so we can know how computers operation and to be able to do some basic tasks (such as making a web page, embedding html widgets in a web page, creating macros, and creating short programs to solve problems).

There are many great resources for learning to code. Here are some to get started with. Find one you really like and stick with it for several days in order to develop some skills. You may want to learn html because that's essentially a formatting language rather than a functional one. Here are some places to try:
Start with html and css (css is also an aspect of formatting) and then you can move into languages that add functionality to your web page, such as javascript, php, python, etc.
This is also a good place to learn html. This one is made to work both on a computer and on a smart phone in terms of format.
This is not as detailed as some of the above, but it is a great introduction to javascript and is specifically designed to be appealing to women and girls.
This is designed for younger children--if you have trouble with some of the others, try this one and see if it works for you.
If you have some programming experience, try this one.

Online IDE
What is an IDE?

A free IDE: