The trick is to use the rem unit introduced in CSS3, which refers to the root element size. In mPDF, 1rem is equivalent to the font size of the HTML body element. All other elements which appear as blocks in the columns, such as headings, subheadings, and info boxes, need to have a vertical size which adds up to an exact multiple of the body text or its line-height. Using rem makes the calculation easier, and also means that changes to body text size will scale other elements proportionally.

CodePen is for Web Designers and Front End Developers. It is an HTML, CSS, and JavaScript code editor in your browser with instant previews of the code you see and write. It is a searchable trove of your own creations, and a world of other people's creations. A place to troubleshoot, to teach, to learn, to test, and to grow.

Antwort offers responsive layouts for Email that both fits and adapts to client widths. Don't underwhelm desktop users with single column layouts that work for mobile. Antwort offers columns on desktop that automatically become rows on mobile. Works on mobile: Mail on iOS and Email on Android. Works in major clients like Hotmail, Gmail, Yahoo! and AOL. Even works in Outlook (2000+). Bulletproof layouts: made with dynamic content in mind. Minimalist in design for maximum customizability.

Mozilla Webmaker wants to help you make something amazing with the web. We’ve got new tools for you to use, projects to help you get started, and a global community of creators — educators, filmmakers, journalists, developers, youth — all making and learning together.

The goal: help millions of people move from using the web to making the web. As part of Mozilla’s non-profit mission, we want to help the world increase their understanding of the web, take greater control of their online lives, and create a more web literate planet.