A few days ago Rok wrote a post about importance of detail for designers. I won't venture into discussion whether 3 pixels change is important only to designers or also to end users, but I do know that I couldn't help moving things by 3 pixels myself in a few instances when I was trying to design something. Instead I will just remind designers that they are entirely capable of implementing design fixes by themselves, with engineers only providing them with the proper infrastructure. I'm sure that nowadays all web designers know about the functionality of modern browsers that enable on the fly editing of HTML and CSS code of a web page.
A designer can polish the looks entirely by himself and just provide the developer with the changes he has done to the HTML and CSS. It would be even better if designers could commit changes straight to repository and deploy them by themselves, but our projects (unfortunately) lack necessary infrastructure for this to be possible.
Just like designers had to learn Photoshop and InDesign many years ago, they have to be proficient in HTML and CSS today. Namely, keyboard and mouse are much more efficient interface between an idea and implementation, than an engineer could ever be.