Responsiveness
Remember to always include this meta tag in the <head> of every html document to assist in making your website mobile-friendly:
Here's a quick summary of responsive units:
- % is relative to the parent element's size
 - VW, VH are relative to the viewport's (browser window or screen) size
 - EM is relative to the current element or parent element's font-size
 - REM is relative to the root element's (<html>) font-size