Gridlex is described as 'Simple. Robust. Responsive. Flexible' and is an app in the Development category. There are more than 25 alternatives to Gridlex for a variety of platforms, including Online / Web-based, Self-Hosted solutions, CSS, Mac and Windows. The best alternative is Bootstrap, which is both free and Open Source. Other great apps like Gridlex are Bulma (Free, Open Source), UIkit (Free, Open Source), Semantic UI (Free, Open Source) and Foundation (Free, Open Source).
Juiced has many of the same layout features that you know and love, but improves upon them with better mobile targeting, custom column ordering, better alignment options, understandable HTML, and less boilerplate styles.
The 960 Grid System is an effort to streamline web development workflow by providing commonly used dimensions, based on a width of 960 pixels. There are two variants: 12 and 16 columns, which can be used separately or in tandem.