The 960 Grid layout is a development of the typographical grid layouts developed in the latter part of the 20th Century for print media by a number of leading graphic designers – particularly Müller-Brockmann in his book Grid systems in graphic design.
The aim of grid systems is to provide a flexible framework for designers to create a coherent organisational structure. The 960 Grid is particularly popular in web design. Through its twelve and sixteen column frameworks, it is particularly well suited for use in laying out modern, responsive web pages and apps.
Some web frameworks, notably Bootstrap with its twelve-column responsive grid layout, make explicit use of the structure of the 960 Grid. There are numerous examples of its use on the web and it’s my personal preference for laying out a site.
For a detailed look at the 960 Grid and links to examples of its use in web design, the website 960 Grid System is well worth a visit and, unsurprisingly, is itself built using the 960 Grid!