[bigiain]

Agreed. I think the fundamental underlying error is not having a reason why a particular elements is fixed or full width.

If you can answer the question "why did you go with a full width header and a fixed width body?", you're probably OK (unless that answer is something like "well, the theme I downloaded from themeforest was fixed width, but the client insisted I use their old header in the new design, so I just mashed it into the template...")

Like most "design errors", I think what the author of e article is ranting about is designs that aren't fully though out - if you've asked yourself the questions "fixed or full width, or both?", "what sized fonts should the forms have?", "how much of the site it going to be long enough to scroll, and do the scroll bars behaviour need to be considered in the design?", then you won't have made these errors, or at least will have good reasons why they are not "errors" but behaviours you chose.