CSS when i add Doctype, the template changes

Hi, can someone please review my site? "aplumbernow.co.uk" i downloaded a template, then changed the code to add text and images, the site is working but when i add doctype the table changes, i haven't made a css file for that website, but is that the only problem? i would like to add css and doctype and for it to work perfectly, i will change the photos myself with photoshop to make it look more professional, but i need help with the css page and maybe xhtml mistakes- needs to stay transitional, thank you very much in advance, Talmania.
p.s when you type A PLUMBER NOW on google it's 2nd or 3rd from the top in the first page.

 

you don't have an external stylsheet but you have embedded styles which have errors.
For example
hight="100%
should be height. Then you don't want to specify 100% as height for the html body maybe.

You have all these spacer.gif instances in the HTML. Take them out, use few CSS rules to create the necessary margins.