CSS treats each HTML element as if it is in its own box. This box will either be a block-level box or an inline box.
CSS has the following positioning schemes that allow you to control the layout of a page: normal flow, relative positioning, and absolute positioning. You specify the positioning scheme using the position property in CSS. You can also float elements using the float property.
Different visitors to your site will have different sized screens that show different amounts of information, so your design needs to be able to work on a range of different sized screens.
CSS frameworks aim to make your life easier by providing the code for common tasks, such as creating layout grids, styling forms, creating printer-friendly versions of pages and so on. You can include the CSS framework code in your projects rather than writing the CSS from scratch.