Jakob Nielsen just published a very interesting article on Auto-Forwarding Carousels and Accordions Annoy Users and Reduce Visibility about carousels but also small promo boxes.
Regarding promo boxes :
- They are considered as ads and thus are ignored by the users
- Being on the right side is not effcient as main focus is on the left side of the screen
- Need to have a clear wording to be meaningful
Regarding carousels/accordions :
- It should stand still to allow users to have the time to read it (think about foreign visitors or low-litteracy users)
- As it moves automatically, users tend to ignored it as they consider it as an advertisement.
- User may not see it as other faces of the carousels may hide the content
- Use a correct wording, here "rewarding lifestyle" or "Siemens appliance" doesn"t mean anything if you are not from Siemens' Marketing Team or worst make people reluctant (I cannot affoard a "Siemens' Applicance")
The main lesson I think is before implementing a trending item (here carousels), think about ergonomy and usability first