Hiring a web design firm can be like buying a car without test-driving it AND not getting to look under the hood. I'll give you the skinny on how to peek. The more you look, the more you'll understand.
The goodies that should be there: references to styles sheets, .css, visually organized, xhtml strict, divs, and compact files.
Looking Under the Hood
It's really simple to see how a website is constructed, simply right-click with your mouse and "view source" or if you're in Firefox, you can download developer tools to really see how it's constructed. You may not understand all the code but you can see who's organized and who's not. Look at all kinds of web pages and you'll get a feel for what's appropriate. The CSS Zen Garden is a good place to start as you'll see how sparse the code on a good design is.
One of the best means for optimizing a site is creating a page that is light in file size, maintaining a good content to code ratio, using relevant content, and filling the page with as much text and links as you can without “spamming” the search engine spiders. This can be a tough balance as we lean toward minimalist design.
Code, as it turns out, needs to be readable by search engine spiders. Poorly written code creates static for the robots in the same way that bad handwriting and poor lighting does for us. They find bad code difficult to analyze and index. CSS and XHTML and good structure under the hood will go a long way toward making your site attractive to search engines. Improving the code organization will ensure that the spiders know what you’re trying to show them.