I contacted canon support and I asked them if it had shutter and aperture priority. They responded (quickly) and sayed
"Thank you for contacting Canon product support about the PowerShot
SD400.
I am very sorry for the misunderstanding. The PowerShot SD400 does not
have a manual mode where you can adjust the shutter speed and aperture.
I apologize for any inconvenience that this has caused you.
I hope this information is helpful to you. Please feel free to contact
us again if you have any other questions or concerns.
Thank you for choosing Canon."
I really wish they would change their website. But it is really misleading. I am glad they responded quickly and honestly. I hope this helps anyone that is planning to get the Canon SD400.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic