it may be a 'NO NO' bit it doesnt stop creatives, designers & flash sites using it which take little consideration of screen sizes anyway... unless it's expanding to 100%.
As a developer you may need to meet the requirments or specifiaction regardless of your perosnal opinion or rules.
If someone specifies something that can't be done, he is demonstrating that he is uninformed. If, after being informed, he still insists, he must be replaced. It is impossible to change the viewing user's computer to meet the bigwig's specs, and illegal to try to do so.
You can approximate a centered page on a browser window, but don't expect it to keep the same proportions or the same vertical positioning on all computers. Web pages expand downward until all of the content can be rendered. Objects with flexible sizes help, but are not always available. And a user with a low screen resolution must always scroll down on a page designed for higher resolution.
We just got a lot of LCD displays that won't display our old web pages without scrolling in both directions. The images are too big.