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Anthony Casalena is a self-professed computer geek, having taught himself computer programming in his early teen years.

But by the time he got to college, he was unhappy with the suite of tools available to build websites. "They were going to be my online identity, and a home for my ideas, and packaging really matters, so I wanted this to look really good," Casalena says. "But I was not happy with the providers. It was all bargain-bin Web hosting."

And so Squarespace, a website design and hosting platform, was born in his dorm room at the University of Maryland in 2003. The founding coincided with lightning-fast changes, such as the migration to mobile, that have made the Web a critical part of daily life for masses of people.

Today, Squarespace, based in New York City, has close to 300 employees and several hundred thousand users around the globe. It hosts and has designed close to three million websites internationally, and its roster of customers ranges from mom-and-pop businesses to big-name clients such as HBO, Michael Kors, and Bottega Veneta.

Casalena was fiscally conservative when it came to building his business. He got started with $30,000 in seed capital from his father in 2004. But it wasn't until 2010 that he took his first round of venture capital-- $38.5 million from Index Ventures and Accel Partners, and by that time, the company was profitable. Squarespace raised its Series C round of $40 million from General Atlantic in mid-April 2014.

And because Casalena wasn't using the money to fund operations, he's still the largest shareholder in the company he built, he says. He used the money to take some of his own investment risk off the table but also to beef up the management team, develop new product features, and increase the scale and reach of the company more quickly.

"I was lucky enough not to need the outside funding, and I could have gone and said, 'These deals are not good enough; I will just wait,'" Casalena says.

Although Squarespace has big competition, from free open-source tools like Wordpress to large companies such as Amazon and Yahoo, and even smaller commercial competitors such as Weebly and Wix, experts say the company has an edge. "Other companies in their space are either easy to use but not that fully featured, such as Weebly, or they are very functional but hard to use, like Wordpress," says Kevin Spain, general partner at Emergence Capital Partners, in San Mateo, California. "Squarespace strikes a nice balance between the two." And the cost ($8 to $24 a month) is relatively affordable.

Adds Andrew Braccia, a partner at Accel Partners who oversaw the Series A investment in 2010: "What we really loved about Squarespace was its ability to extract the complexity of building a great Web presence, and that it can do so with a finished product that is beautiful and represents who the customer wants to be on the Internet."

With that in mind, Casalena says the introduction of Squarespace 6, the first entirely rewritten software since the launch of the platform with Squarespace 1 in 2004, positions the company well for growth in an increasingly mobile world. Released in 2012, the new platform has more native apps, templates, and responsive design that allow for distribution of content across different mediums, as well as image synching according to device and the ability to store and exhibit pages in the absence of a Web connection.

"We know about your images and blog posts and pieces of content and pages, and we can put them into any medium you want them put into," Casalena says.