Emily — thanks for this article. I found it very helpful and interesting. As a web designer myself I find it challenging to find, and stick to, best practices when creating designs for the web. You mentioned here that your team chose to create mock-ups at the smallest breakpoint for each target size. Did you create static grid templates to use as you worked on your design? If, so how did you determine the size of your 12-column grid and the spacing in between? Between designing for percentages on the web but having to mock-up static designs using pixel measurements I find there to be quite a disconnect between my design layout and how our developers implement them. Do you have any suggestions on a grid template that I could use to mock-up static designs. Or do you manually create custom grid templates for your projects?