For fixed width websites, People are often unsure of the ideal width to have their site set to.
This is a crucial decision to make. As the size of a users screen or resolution could make parts of your site be missed off the sides of his/her screen. Making it necessary to scroll left to right to read full width lines of text or to see large images. Either way, It's good to get a fine balance between being wide enough to look nice without having to scroll up and down too much, because your wrapped text looks squashed between elevator doors...

At present, 36.65% of visitors to this site have the resolution of 1024x768, This means a page width of 1000px is a bad idea..

Below that, Only 3.5% of users have the next common resolution down, Which is 800x600.

Showing that the resolution of 1024px wide max is a wise choice.
But don't set your site to that width without considering the page rarely goes to the edge of a users screen.
 They usually have a vertical scroll bar in place making the ideal width pixel resolution for most websites would be [size=18]968px[/size].

Yeah any less than that tends to look very amateur. Like from a template or quick "blog maker".
Very narrow sites are suited to simple sites, any less than 900 would look silly.

Liquid layout is also good but that's usually reserved for sites with masses of information to display. On a relatively simple company site, they would struggle to fill that space. Fixed width sites are best in that situation.

The size would be set on the containing element which contains all the website's content. This value would be set from the associated style sheet.

To centre the now, 968px wide container, you'd use:
margin-left:auto;
margin-right:auto;
In your CSS's body attribute.