Media queries were introduced into the web development world by the arrival of CSS3. They now form the foundation for responsive web design. With media queries, you can create separate layouts for different screen sizes like smartphones and tablets. This article is a basic overview of how media queries work.
CSS3
Actual Size Online Ruler
This actual size online ruler is powered by HTML5 and JavaScript. Using the canvas element, it adjusts/calibrates itself based on the options you select.