Where best to place alert/notifications on a website?

Question

What do I mean by alert/notification?

Example is an instant-messaging application, on the event when a user/friend comes online, you receive an alert that they are online - this alert is what I'm talking about.

How is this done on the desktop?

On desktop applications pop-up alerts/notifications appear bottom-right corner on Windows and top-right on MacOS X (for me anyway).

What makes sense for websites?

Say you're designing an IM tool that is website-based (used within a browser). Would you replicate the alert behaviour found in operating systems like Windows, or would you do something different.

My thoughts are that users are most focused on the area top-left* when browsing websites, so does it make sense to display an alert bottom-right? But at the same time users are used to alert behaviour based on how their OS works, does this really matter though?

Where would you place alerts on a webpage?

*For the majority of web users (ignoring right-to-left languages for now).

Note: This isn't strictly a programming question, and if I could afford it, I would hire a professional UI designer to figure this stuff out :-)

Answer 1

You want to do what the user is already comfortable with. So sites like facebook has a bottom right notification which works well. The user is already comfortable with that no need to change it.

That is of course, notifications that do not require immediate attention. bottom right notifications are not designed to be immediately noticed and acted upon by the user.

If you need the user to stop and react to the notification immediately then center or top left might be better.

Answer 2

Personally, I like the way Stack Overflow does it, with a bar in a contrasting colour at the top.