Here's the flow I think of...
- The designer on the project creates the UI spec.
- The UI developer takes the UI spec and creates HTML rendition of the UI spec.
- The HTML produced is the result of negotiations and agreements between the designer and the UI developer. Everything may not be possible and sometimes UI developer will have to modify the designs to be able to actually make it work in a web page. But the designer should always be aware of the changes the UI developer plans to make, and they should discuss to see what are the possibilities.
- He/she can use free tools like Firebug (Firefox plugins) to edit/debug CSS/HTML live in the web page and compare their work to the UI spec using Pixel Perfect compare their to validate it
- The development team then takes the HTML code and builds the application using it. They don't have to worry about being pixel perfect as long as they don't change any "style" elements/code
So, it is the UI developer's responsibility to make the page components pixel perfect. With this process being pixel perfect can become much simpler.
Being Pixel Perfect - Part 1 | Part 2 | Part 3 (what to make pixel perfect?) | Part 4 (How to make it pixel perfect?) | Part 5 (How to test?) | What makes a great user interface? | What are our biggest opportunities? | Part 6 (Why aren't we pixel perfect?) | Part 7 (Building front-end development skills) | Part 8 (Standards anyone?) | Part 9 (web template for dev teams) | Part 10 (new brand guidelines are available now!) | Part 11 (top developer tools for front-end development)