Also bear in mind that when using high resolution laptops some users increase the default font-size. This can affect the feel of your page if everything else is rigid.

I agree with StoutFiles

The most popular site on the planet right now, Facebook, uses 980px.
CNN also uses 980px wide.

I tend to look at the sites that have big traffic and test.

Why reinvent the wheel...

I'm looking for the maximum fixed width I can go on a websites and still be compatible across almost all resolutions/monitors. I usually stay around 900px but I was wondering how much further it can be pushed?

1003 pixels wide.

some users increase the default font-size. This can affect the feel of your page if everything else is rigid.

I'm reading this topic in IE8 with "Larger" font size and 125% zoom level. There's a reason those tools are/can be directly clickable in the browser window.

But then flexible sites that expand all the way on a wide screen look pretty silly also.

Not only look silly, they are difficult to read. I forget the recommendation, but main text shouldn't be wider than say 800px so readers don't have to scan side to side, which is tiring and conducive to losing one's place.

At the moment I have a 1280 x 768 monitor and am looking at WebmasterWorld in a much reduced window otherwise it just looks silly and hard to read.

At home I have a 1024 x 768 and sometimes some pages of WebmasterWorld extend out wider than that which is also a pain.

Whatever you do, please don't go with the fashion of specifying fixed-size fonts.

On my 22-inch 1680x1050 monitor, the "font-size: 9px" fonts are so tiny I'm often forced to zoom-scale with the browser, which makes the graphics all bitmap-ugly.

I know that tiny fonts make layout seem easier, but if they make the physical size too small on large resolution monitors, it does the site no favours from a usability point of view.

What UserFriendly said...

The fact is, screens aren't getting bigger. They're getting more varied. When anything from an iPhone to a Mac has a browser, you really don't know how big the AVAILABLE screen is.

And you don't know how big a window the client is using on that screen.

And you don't know how many times the user clicked "control-plus" because his 40-year-old eyes couldn't see what's so clear to a 23-year-old eagle-eyed professional graphics geek.

A page that doesn't flow well at 400 pixels just isn't User Friendly. For any combination of these factors.

The most popular site on the planet right now, Facebook, uses 980px.
CNN also uses 980px wide.

I tend to look at the sites that have big traffic and test.

Why reinvent the wheel...

news.bbc.co.uk seems to use 974 pixels width.

When I first started making web sites, 800x600 was considered the leading edge standard monitor resolution, and 640x480 was very common. My fixed-width sites ended up being about 590px wide.

Eventually, 640x480 traffic died out (it took forever, because I get a lot of people visiting from libraries) and 1024x768 became common.

I see 1024x768 dying out now, but it's still a significant enough portion of my traffic that the latest site I did is 975px wide.

Netbooks? A fad that is also dying as people realize they don't live up to the hype, and they get more portability, utility, and battery life from their smart phones and iPads.

As for mobile browsers -- don't worry about it. The notion of having a "mobile site" will seem antiquated in 18-24 months. Any mobile device worth owning has a double-tap or some other method for enlarging and reducing portions of the page. And with pixel densities and bandwidth on the rise for mobile devices, it makes the mobile/desktop divide even blurrier.

Apple's new Retina display for the new iPhone can render the entire New York Times home page without scaling.

Spending time and money making a mobile site for a new project these days makes as much sense as making a WAP site.

You're better off spending your time and money developing compelling content.