Twitter unveiled an overhauled website on Tuesday that that lets people more easily sift through the growing mountain of micro-messages and creates more opportunity for advertising.

"A new bird, a new experience, a new twitter.com starts rolling out today," Twitter co-founder Evan Williams said as he showed off the new design at a press event at the firm's headquarters in downtown San Francisco.

"It's an easier and richer experience, and a better way to discover what is new in your world."

A details pane was added to the right of the timeline of "tweets" that has long been a mainstay on Twitter profile pages.

Twitter users can see pictures, videos, and other information from any particular micro-message quickly in the side-panel without having to navigate away from the timeline showing the ongoing stream of tweets from people they have signed on to follow.

"This lets you drill down and get more information without ever losing your timeline," Williams said.

"No more clicking away from the page. You get instant loading of pictures, playable videos -- you can see more of conversations in context."

The overhaul, which was code named "Phoenix" in keeping with Twitter engineers naming internal projects after birds, will be rolled out gradually in the United States and gradually extended to all of the service's 160 million users worldwide, according to product manager Kevin Cheng.

"We are going to take it easy to insure the stability," Cheng said of the global rollout of the new Twitter page. "We are not going to give it a time frame; just watch how it goes."

About 370,000 people are signing up daily for Twitter, and users fire off more than 90 million tweets each day, according to Williams.

"As you can see, it is going off the charts," Williams said. "We've been focusing a lot on infrastructure, performance and reliability. The growth curve is obviously not easy to handle."

The new design made it simpler to embed pictures or videos directly on Twitter, which made deals with 16 firms including YouTube, Flickr, Vimeo, and TwitPic to display content from those websites.

Twitter engineers said they were very careful to preserve the spirit of the microblogging service while adding features that smack of social networking website Facebook.

"Keeping the simplicity of Twitter was a top priority," Williams said.

The classic timeline at Twitter has been made cleaner and infinite, meaning people can continuously scroll down pages to see more tweets. Search and "retweet" buttons were moved to more intuitive locations.

"If you never open the details pane a single time, this version of Twitter will be better for you," said vice president of products Jason Goldman. "It's a better Twitter."

Twitter users can opt to leave the details pane closed.

Those who use the details pane will find they can get glimpses at profiles of tweeters and strings of exchanges in context along with views of what people have linked to tweets.

Approximately 25 percent of tweets contain links to online content, according to Goldman.

"That means 250 tweets per second are being produced with links in them," Goldman said. "The experience of getting those in your timeline has been historically quite poor."

The details pane opens up revenue possibilities for Twitter by adding on-screen "real estate" that can be used for pictures, videos or other advertising linked to tweets for businesses or brands.

"A tweet about a movie could be immediately linked to a trailer," Williams said. "We have yet to show it to advertisers, but we think they will be really excited."

Twitter in May banned outside advertising in the stream of messages at the microblogging service.

Twitter runs a "Promoted Tweets" advertising service that allows companies and others to place 140-character-or-less messages known as "tweets" at the top of a page of search results.

Forrester Research social media analyst Augie Ray called the overhaul "significant evolution" that bodes well for Twitter.

"Improving consumption of Twitter-based content is important not just for Twitter, but for interactive marketers as well," Ray said.