I'm not a real web designer, just a hobby, but it seems important to have a doctype to conform to web standards. How do you know which doctype standard to use for your site.

For example on the site I'm designing now, www.standrewcarolstream.org/test.html

I'm currently using the HTML 4.01 transitional doctype and everything shows up fine in I.E 6 and Firefox. It appears most sites use an XHTML doctype, but when I tested my site with that doctype my page didn't display properly in Firefox. For example when the xhtml doctype was used my navigation and content <div> where not centered like the rest of the page leaving the navigation and content on the left margin.

Thanks,
Chris

It appears most sites use an XHTML doctype,

Not hardly. The use of the XHTML doctype is growing, but I see far more that are still using HTML 4.01 Transitional.

but when I tested my site with that doctype my page didn't display properly in Firefox.

That's because there are more stringent rules to using the XHTML doctype, and Transitional is slightly more forgiving than Strict. Still, you have to follow the rules required for that doctype.

For example when the xhtml doctype was used my navigation and content <div> where not centered like the rest of the page leaving the navigation and content on the left margin.

How did you code it to achieve centering ? If you used 'div align="center"' it was incorrect for XHTML.

If you're not ready to code to the higher standards of XHTML, then stick to HTML 4.01, but use HTML 4.01 STRICT instead of Transitional. Strict forces you to use cleaner code and follow some real rules.

yurp what she said

have a go with the validator.w3.org W3 validatior, stich it in tellit to check at xhtml transitional, and it will show you all your bits which are wrong and can help you learn. and then when u code next time you use the xhtml rules and you will get less validation problems