I have written down some rule of thumbs you should check before incorporating a CSS Designer or Author. They are not that tight-check technical rules that can be measured one by one, but to get the whole picture, i suggest the following:
These are my 3 cents today. XHTML/CSS can be very powerfull within a webproject even over version boundaries. But a bad made Design can really kick ass as well. Read on for the Details.
Most Users do still use a Windows PC and so this is very much often the most of the design audience to check the overall valid and interoperable CSS Design against. A CSS Designer should be very firm within this windows-domain (at least historically) and therefore it can be an argument, if the designer her or himself is a user of such a system. At least this is important for the current status quo. Additionally, it is very OK if the CSS Designer owns an Apple Computer and can check the Design on that Plattform, too. And open up: Those Designs should be checked on Linux driven Plattforms as well to name it. Therefore this is not a per-se argument, but you should take care with postulations like “I design and work on Apple only”. And do not forget: Apple is Evil ätz well.
A CSS Design is something static and a static DOM and CSS should be delivered. If such an author makes use of scripts for something that is not needed in the design, this is really bad practise and a payload of upcoming problems if you want to integrate the DOM/CSS Design into a CMS or a more complex page. At least if this has not been clearly defined through all the departments. Keep in mind, XHTML/CSS is the skin of the output, you can lay below that whatever you want. So it is very important that it is plain, solid and it can be trusted.
A designer that is not able to create CSS in a modular and therefore useable way, might be a superhero in his local neighborhood but is not a CSS Designer at all. CSS is very powerfull in terms of the inbound hierachie and all this power should be taken to create modular and therefore powerfull XHTML/CSS templates. A CSS Designer must ask the right questions before beginning the job to clarify how the markup is used later on. The design should be able to handle multiple type of document fragments with ease etc. pp.. If such a Designer has a narrow view on the screen seeing it as a single sheet of paper, then he should start painting but not authoring the CSS and writt’en the DOM – if you ask me.