I get a "Page not found" error when I enter a valid profile URL
There are a few things you can check when this happens:
Is the profile URL you are using actually a personal profile and not a Facebook Page? Pages should instead use the Like button
Does the person whose profile you are using with the Follow button have following enabled? You can check this by having the person check their Follower Settings and enable them.
Use the alternate profile URL with that person's User ID instead of their username. For example http://www.facebook.com/4 instead of http://www.facebook.com/zuck.
What are the different layout types?
There are three options:
Layout Default Sizes
standard
Minimum width: 225 pixels.
Default width: 450 pixels.
Height: 35 pixels (without photos) or 80 pixels (with photos).
box_count
Minimum width: 55 pixels.
Default width: 55 pixels.
Height: 65 pixels.
button_count
Minimum width: 90 pixels.
Default width: 90 pixels.
Height: 20 pixels.