SAN FRANCISCO Twitter revamped its website on Thursday to make the microblogging service easier to use and to help companies better showcase their brands.

The new version of Twitter, which the company is gradually making available starting on Thursday, will feature a new look and feel and faster performance, the company said.

The redesigned website comes as Twitter is taking steps to introduce more advertising on the site and as Twitter faces increased competition from Web giants Facebook and Google Inc .

We have to provide the simplest and fastest way for people around the world to connect to everything they care about, Twitter Chief Executive Dick Costolo said as he introduced the new version of the site at an event at the company's future headquarters in San Francisco.

Costolo appeared alongside Twitter co-founder Jack Dorsey, who returned to the company in March as executive chairman to oversee the company's product design and development efforts.

Twitter allows people to send 140-character messages, or tweets, throughout the network of over 100 million users. It is one of the Web's most popular social networking services, along with Facebook and Zynga.

In October, Apple Inc integrated Twitter's service directly into the software that powers the popular iPhones. Since then, Dorsey said, the number of monthly sign-ups for Twitter have increased 25 percent.

Even as Twitter continues to grow, it faces fresh competition from Google, which introduced a social networking service with capabilities similar to Twitter earlier this year.

On Thursday, Facebook, the world's No.1 social networking service, announced a new feature that allows its users to visit a website and subscribe to updates from celebrities, journalists and other public figures.

The new version of Twitter seeks to simplify the service and to make it easier for new users to understand various Twitter-specific features, such as the # symbol that is used to search for topics on the service.

Twitter should be useful by those who know the shortcuts, and also equally useful by those who don't really use the shortcuts, said Dorsey.

A new Discover section of the website highlights the most popular topics on the site based on each user's location and interests.

The new version of Twitter also features a revamped profile page, in which a company can customize the look of their brand and highlight specific content, such as videos or photos. Previously, the profile pages displayed a chronological list of the company's most recent Tweets.

Twitter said that 21 brands, including General Electric and Pepsi, have already revamped their profile pages to take advantage of the new capabilities. Twitter will gradually make the new profile page features available to all its users.

For marketers, this is something that they've been asking for of us for a while, Adam Bain, who leads Twitter's revenue efforts, said in an interview after the briefing.

Twitter is taking steps to build a profitable business on top of its popular service. The company began showing ads on limited parts of the service in 2010 and is expected to generate about $140 million in ad revenue this year, according to estimates by industry research firm eMarketer.

The company said it has more than 2,400 advertisers and it expects to launch an advertising system early next year that will allow companies to quickly create marketing campaigns on Twitter.

Twitter hosted Thursday's event at its future headquarters in San Francisco, which are currently under construction and which Twitter plans to move into this summer. The building will accommodate far more than the company's current staff of 700 employees, Costolo said.

It holds thousands of people, he said of the office. We're going to need all this space to scale the company to support the growth of the product we've been experiencing over the last year.

(This version corrects last paragraph to show number of Twitter advertisers total more than 2,400 not 3,400)

(Reporting by Alexei Oreskovic; Editing by Derek Caney, Carol Bishopric)

Apple inc. Software Twitter