diff --git a/guide/english/css/css3-flexible-box/index.md b/guide/english/css/css3-flexible-box/index.md
index 3c952b374f..54da52db98 100644
--- a/guide/english/css/css3-flexible-box/index.md
+++ b/guide/english/css/css3-flexible-box/index.md
@@ -61,14 +61,16 @@ The `flex-flow` property is shorthand for `flex-direction` and `flex-wrap` in th
 
 #### More Information
 
-- To get a complete understanding of Flexbox, read <a href="https://medium.freecodecamp.org/understanding-flexbox-everything-you-need-to-know-b4013d4dc9af" target='_blank' rel="nofollow">Understanding Flexbox Everything you need to know</a> on the FreeCodeCamp Medium page.
+- To get a complete understanding of Flexbox, read <a href="https://medium.freecodecamp.org/understanding-flexbox-everything-you-need-to-know-b4013d4dc9af" target='_blank' rel="nofollow noopener">Understanding Flexbox Everything you need to know</a> on the FreeCodeCamp Medium page.
 
-- For an interactive guide go through <a href="https://medium.freecodecamp.org/the-ultimate-guide-to-flexbox-learning-through-examples-8c90248d4676" target="_blank" rel="nofollow">The Ultimate Guide to Flexbox — Learning Through Examples</a>
+- For an interactive guide go through <a href="https://medium.freecodecamp.org/the-ultimate-guide-to-flexbox-learning-through-examples-8c90248d4676" target="_blank" rel="nofollow noopener">The Ultimate Guide to Flexbox — Learning Through Examples</a>
 
 - A great visual guide to Flexbox is provided by [JavaScript Teacher](https://medium.freecodecamp.org/@js_tut) on the FreeCodeCamp Medium page: [The Complete Illustrated Flexbox Tutorial](https://medium.freecodecamp.org/the-complete-illustrated-flexbox-tutorial-d35c085dbf35).
 
-- Yet another great visual guide that is in-depth but easy to follow can be found in <a href="https://css-tricks.com/snippets/css/a-guide-to-flexbox/" target="_blank" rel="nofolow"> A Guide to Flexbox</a> by <a href="https://css-tricks.com" target="_blank" rel="nofolow">CSS-Tricks</a>
+- Yet another great visual guide that is in-depth but easy to follow can be found in <a href="https://css-tricks.com/snippets/css/a-guide-to-flexbox/" target="_blank" rel="nofolow"> A Guide to Flexbox</a> by <a href="https://css-tricks.com" target="_blank" rel="nofolow noopener">CSS-Tricks</a>
+
+- Also check out <a href="https://developer.mozilla.org/en-US/docs/Learn/CSS/CSS_layout/Flexbox" target="_blank" rel="nofollow noopener">Flexbox on MDN</a> to get a understanding of the fundementals.
 
 - I suggest working out while playing the game [Flexbox Froggy](http://flexboxfroggy.com)- [Guide](https://github.com/thomaspark/flexboxfroggy)
 
-- <a href="https://flexbox.io/" target="_blank" rel="nofolow">A simple, free 20 video course that will help you master CSS Flexbox! by Wes Bos</a>
+- <a href="https://flexbox.io/" target="_blank" rel="nofolow noopener">A simple, free 20 video course that will help you master CSS Flexbox! by Wes Bos</a>