Read able is a Google Chrome / Opera extension that makes it easier to focus on particular parts of a website, for example long text by highlighting only a part of it and graying out the rest. It was designed especially for people with ADHD and others, that find it difficult to focus on and read a long body of text without any visual highlighting the part that they are currently reading.
You can either install it from Chrome Web Store or download and pack the files yourself from here.