There is an underlying principle to designing layouts effectively and that is the humble grid. Grids are everywhere and you’ve most likely not noticed them or paid much attention to them, that’s because a grid isn’t there to be the star of the show. The grid is there to guide you in creating the star.
This guide is based on Mac commands. Windows syntax is slightly different and covered in-depth here.
Web performance budgets are a hot topic right now and for very good reasons. We as designers have been let off the lead recently (relatively free from not doing things because a certain browser can’t) and are having a blast using big high-res imagery, background videos and the font-stack of our dreams. Unfortunately all of this comes at a cost, and that is a monetary one to the user (data isn’t cheap!)