Can I be notified when someone visits a certain website?

You can setup a smart campaign that says...

Smart List
Trigger - Visits Web Page (find the page you want to track in the list)

Flow
Alert email (in the send to select none, then place your email in the "other emails" box

One thing to be aware of, this will only work if that person is a known lead. If not, or if that person clears their cookies/uses a different web browser, you won't be notified until that person becomes known.

Also, you'll get a lot of emails when that person does visit unless you set it to only run through once a day or something.

The Visits Web Page trigger won't work if they visit a website that doesn't have munchkin code on it. 

I have been able to send Anonymous Website Visitor Alerts using the Visits Web Page trigger in the smart campaign's smart list section and the following Send Alert flow action in the flow section.

Choice 1: If 'Is Anonymous' is true then:

Email:  'Website Visitor Notification'

Send To: 'None'

To Other Emails: 'xxx@xxx.com'

Default Choice:

-- Do Nothing --