A fixed width site is one where the main wrapper is set to a specific fixed width independent of the user agent’s display resolution. A common and thoughtful fixed width is 760 pixels, a size that ensures users with 800×600 resolution monitors have close to full window viewing without bothersome side-scrolling.

Advantages

  • The main readable content area is tightly controlled without having to set minimum-maximum width (which isn’t universally supported, anyway).
  • Fixed width layouts are sometimes easier to style depending on the effect you’re after. Some visual designs can only be achieved in a reasonable manner with a fixed width layout.
  • Based on the example width above — 760 pixels — the typical main content area will be in my opinion an ideal width for optimum readability.

Disadvantages

  • My valuable “ideal width for best readability” pro-listing above can go bad if the text is enlarged greatly since the line-width-to-text-size ratio doesn’t increase along with text resizing. Do note, though, in a good design, this is only a problem if the text is huge.
  • People with small monitors (640×480 pixels) will end up with a horizontal scroll bar on a 760 pixel fixed width site. This is a very uncommon problem.
  • A 760px fixed width site can look too narrow on large screen displays.
  • The narrow width can limit the reasonable number of columns and content, but this may actually be a pro. Think forced moderation.

Some Fixed Width Advice

  • Place your fixed width content on the left hand side of the page so on a typical site 640×480 pixel monitor users won’t have to side scroll to read the site’s primary content.
  • Be sure to provide a handheld style sheet to accommodate smaller devices. Supplying projection and TV media-type style sheets may also be a good idea.