Google executive Marissa Mayer, the web giant's twentieth employee and first female engineer, pulled back the curtain Tuesday evening to reveal why Google's stark white homepage looks the way it does.

Mayer, Google's vice president of local, maps and location services, was the gatekeeper of Google.com for more than a decade and helped shape what Google's millions of users see and experience when they search online. Though some have attributed Google's design to Mayer's own tastes, Mayer said Google.com's layout, which has changed little since its inception, owes its stark look to Google co-founder Sergey Brin and his limited knowledge of HTML, a markup language for websites used to assemble text and other content to create webpages.

Mayer said Brin once explained to her why Google's homepage was so blank. When he was first building Google, "We didn't have a webmaster and I don't do HTML," she said he told her.

"He put together the simplest web page he could to test out the search engine back when he was Ph.D. student," Mayer said during an interview with Bloomberg Businessweek editor Josh Tyrangiel at the 92nd Street Y in Manhattan. "The first version didn't even have search button because the return button worked just fine. We just kind of stumbled into it."

Mayer noted that users were initially befuddled by the plain white page they found on Google.com. It was unlike many websites of the late-1990s that "flashed, revolved, and asked you to punch monkey." People couldn't figure out how to use the search engine because Google.com was so simple.

In Google's first user study, Stanford University students asked to search on Google would sit for 45 seconds staring at their screen, unsure what to click or how to search, Mayer recalled.

"I'd ask them, 'What are you waiting for?'" Mayer said. "They'd say, 'I'm waiting for the rest of it.' The blank homepage was so out of context in 1999 that they were just waiting for the rest of it."

Google needed a way to signal to users that the page was finished loading and ready to be used, Mayer explained. The solution? Putting at the bottom of the Google.com homepage a small copyright notice -- one that serves no legal purpose whatsoever, but functions as a cue that it's OK to start searching the web.

That page now sees so much traffic -- more than a billion unique users a month, according to some estimates -- that placing an ad on Google.com would be in the "eight figure range" per day, according to Mayer.