does anyone use tools to check websites? for example i would put in a url and it would check for load speeds, w3c compliance, broken links, browser version compatibility and OS compatability etc etc

if so what do you use and why is it good?

Yahoo have a tool called YSlow which will look at performance. Not sure about broken links but there's a firefox extension that'll look at a page and highlight them; I don't seem to have it installed any more but should be easy to find. Not sure about the other things you asked, I doubt there's anything that'd do that.

goddamn you spamming fuck, fuck off

There are many ways to judge a website's quality, most of these ways cannot be reproduced via a computer algorithm. The w3c validator is an example of an exception to this - but even so, there is no law or anything that says your website must be w3c compliant, just as nothing forces Internet Explorer to be w3c compliant. So whether you make your site w3c compliant is totally your choice. W3c compliance means you won't be able to use a few techniques/tags/attributes that are fully supported by major browsers, or by a particular browser. Use your brain, I guess, and don't bend over backwards to satisfy some unintelligent computer program.

Browser compatibility and OS compatiblity are just things you have to try out yourself on various systems. Even when a program tries to emulate the renderer of IE6, etc... it often does not inherit the wonderful nuances of IE's behaviour, such as the peek-a-boo bug when you resize the window or click something.

There are many ways to judge a website's quality, most of these ways cannot be reproduced via a computer algorithm. The w3c validator is an example of an exception to this - but even so, there is no law or anything that says your website must be w3c compliant,

well, arguably it doesn't judge quality, just compliance to the HTML specification

As mentioned, compliance of your website markup to standards is an entirely different thing to the quality of the website. Or rather, its only a small step towards it (and invisible to end-users as long as compliant/non-compliant code generates the same results).

I usually do markup in XTHML as it forces me to do strict XML markup and not be a lazy prick and rely on browser's letting poor markup through.

That w3 site is so annal retentive... my default page which has one line "hello world" managed to clocked 2 errors and 3 warnings LOL - WTF?!?

but i do need to make sure the colours used are web safe etc

http://www.ficml.org/jemimap/style/color/wheel.html

but i do need to make sure the colours used are web safe etc

Just use 16 colour GIF and you're set.

That w3 site is so annal retentive... my default page which has one line "hello world" managed to clocked 2 errors and 3 warnings LOL - WTF?!?

Yeah it gets rather pedantic at times. It likes you to have character encodings listed and it even bitched at me because I didn't have a <title> tag.