Web pages should be well laid out to improve navigation for the user.
Also for navigation purposes, the sites page layout should also remain consistent on different pages.[12] When constructing sites, it’s important to consider page width as this is vital for aligning objects and in layout design. The most popular websites generally have a width close to 1024 pixels. Most pages are also centre aligned, to make objects look more aesthetically pleasing on larger screens.[13]
Fluid layouts developed around 2000 as a replacement for HTML-table-based layouts, as a rejection of grid-based design both as a design principle, and as a coding technique, but were very slow to be adopted.[note 1] The axiomatic assumption is that readers will have screen devices, or windows thereon, of different sizes and that there is nothing the page designer can do to change this.
Accordingly, a design should be broken down into units (sidebars, content blocks, advert areas, navigation areas) that are sent to the browser and which will be fitted into the display window by the browser, as best it can. As the browser does know the details of the reader’s screen (window size, font size relative to window etc.) the browser does a better job of this than a presumptive designer. Although such a display may often change the relative position of major content units, sidebars may be displaced below body text rather than to the side of it, this is usually a better and particularly a more usable display than a compromise attempt to display a hard-coded grid that simply doesn’t fit the device window. In particular, the relative position of content blocks may change, but each block is less affected. Usability is also better, particularly by the avoidance of horizontal scrolling.
Responsive Web Design is a new approach, based on CSS3, and a deeper level of per-device specification within the page’s stylesheet, through an enhanced use of the CSS @media pseudo-selector. source: wikipedia
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