Pros/Cons of PSD mockups vs. HTML mockups

I’ve read some articles (this one and this one) recently that are opening my eyes to HTML mockups as opposed to the usual PSD mockups.
In the article they cite certain pros:
Changes are a lot faster (including changes to c…
iPhone/iPad: Do people use landscape mode?

I noticed that I nearly never use landscape mode except when I have to (apps with fixed orientation) or when watching videos. But of course I don’t want to consult customers based on my own behavior. So does anybody know if t…
iPhone/iPad: Do people use landscape mode?

I noticed that I nearly never use landscape mode except when I have to (apps with fixed orientation) or when watching videos. But of course I don’t want to consult customers based on my own behavior. So does anybody know if t…
Best practices for online help

we’re currently developing a fairly complex web portal. To improve the user experience, we want to provide a context-sensitive online help system that can aid the user in understanding certain aspects of the site.
In our case…
Usability testing for open-source projects?

I’m working (slowly) on an open-source project, and I was hoping to do some usability testing once it’s a bit further along. Also, hopefully the GIMP devs will notice this question ;-). I’m not sure how much can be done for $…
Scrollbar on the left

Is there a deep study that suggests to place a scrollbar on the right? Personally I move it to the left whenever possible (Firefox allow this, as well as xterm and emacs).
I know that placing a scrollbar on the left is consi…
Scrollbar on the left

Is there a deep study that suggests to place a scrollbar on the right? Personally I move it to the left whenever possible (Firefox allow this, as well as xterm and emacs).
I know that placing a scrollbar on the left is consi…
OK/Cancel on left/right?

Should OK button be on left of Cancel button or vice versa?
Are there any studies suggesting either of the solutions?