There are a two reasons behind the development of: downtownsanfrancis.co

Those reasons are (in no particular order):

• A keen passion (obsession ?) for creating websites using the Joomla!™ Content Management System (CMS)
• To demonstrate a point made in another Joomla!™ website where domain name extensions can be leveraged to help create a full word or phrase - here we use downtownsanfrancis.co to create the phrase Downtown San Francisco (Can you see it now ?) Downtown San Francis dot co

.co ( dot co) is the country code Top Level Domain (ccTLD) extension for:

• Colombia

But is often used to:

• Indicate, or represent: 'Company' (BusinessNameAnd.co = i.e. 'Business Name and Company')
• Indicate, or represent: 'Commercial' - as in a commercial business although perhaps .com (dot com) is a more familiar extension for 'Commercial'
• Finish a word or phrase that ends in 'co' - such as
  • 'San Francisco'
    • SanFrancis.co / SanFrancis(dot)co

If you want to read more about such use of domain names you might like to visit Domain name hacks where you can (perhaps) think of your own catchy domain name idea.

Of course there is an alternative to this harmless type of "hack" - the alternative is much, much less honest.