A useful list of usability considerations from Smashing Magazine. Read the full article here.
The ideal search box is 27 characters wide
Usability testing on just five users will uncover about 85% of all problems with your website
The ideal position for labels in forms is above the fields because users scan the form downwards as they read, so following the label to the field below is easier than finding the field to the right of the label.
Using a picture of a face looking directly at you will detract from any copy you have on the page, as we naturally gravitate to looking at faces. Making the face look away from the lense - ideally towards your copy - will focus the attention on your message.