PUBLIC MARKS from decembre with tags browser & tutorial

If you were attentive you should see that the line width: calc( 12.5em ) is the trick here. Why? Let’s see all these widths like in pairs – exactly what we need browsers to do. The first pair is width: 80% (content) and width: 16.666% (sidebar) that does the job in calc() incompatible browsers, which will just ignore calc(). It is the callback (backup). It means that the minority of website visitors will see narrower sidebar on narrower viewports. And that should be perfectly fine for people using older browser versions. The second: width: calc( 100% - 15em ) and width: calc( 12.5em ). This is for newer browser versions which will override the previous width definitions

Let's take a look at what it takes to build a grid overlay with CSS. It will be responsive, easily customizable and make heavy use of CSS variables (known more accurately as "CSS custom properties"). If you aren't familiar with custom properties, I'd highly recommend reading What is the difference between CSS variables and preprocessor variables? and watching Lea Verou's enlighting talk on using them. This grid overlay that we're building will consider a developer tool, as in, a tool just for us, not really our users. So, let's not worry too much about browser support (If you do care, check out caniuse… data on custom properties). While it's impossible to preprocess custom properties to behave exactly the same as native support, if you use them just like you would preprocessor variables, tools like the postCSS plugin cssnext can transform them into CSS compliant with older browsers.

How to modify Firefox's configuration (about:config) All this "advanced config" talk got you worried? Fear not, my friend. Here's the deal: Firefox's configuration is a long list of keys and values. To view this list, type about:config into the Firefox ad