AT&T and Yahoo! have announced an expanded alliance that includes revenue-sharing for online advertisements on both PCs and mobile devices. Under the new partnership, Yahoo! will provide “a new look and feel” for the att.net portal, powered by Yahoo!. The new portal will be available to new AT&T broadband customers in the second quarter, existing customers will see the upgrade later this year. AT&T wireless customers also will see search and display advertising provided by Yahoo!.

“Our goal is to connect our customers to their worlds, wherever they live and work,” said Randall Stephenson, chairman and CEO of AT&T, in a statement.

Meanwhile Yahoo! Co-Founder and CEO Jerry Yang remarked, “Since 2001, the AT&T-Yahoo! alliance has been a benchmark in both the telecommunications and Internet industries. The combination of Yahoo!’s innovative mobile and PC applications and advertising solutions, with AT&T’s leadership in customer connectivity, mobility and robust networks once again raises the bar for the entire industry and further establishes Yahoo! as a starting point for consumers on the Internet.”

Although both companies announced the expanded partnership to include revenue-sharing, detailed financial terms were not disclosed.

In a separate announcement, Yahoo! has named former VeriSign executive Aristotle Balogh as its new chief technology officer.