Today’s a big day in Silicon Valley, earnings-wise, because it’s time for Yahoo to show its hand.

There’s a lot at stake when the struggling Internet pioneer reports quarterly earnings today at 2 p.m. Pacific Time. For the past two months, Yahoo has said its online advertising business has been cruising along, despite a shaky U.S. economy. The company has pointed to that strength to resist Microsoft’s takeover bid of $31 a share.

In January, Yahoo forecasted first quarter ad sales in the range of $1.28 billion to $1.32 billion, according to Thomson Financial. If Yahoo beats those numbers, especially if it shoots far beyond them, the Redmond behemoth would face pressure to up its offer.

Google’s unexpectedly huge earnings last week –- net income of $1.31 billion -- also reinforced investors’ faith in Yahoo. That’s another factor in whether Microsoft feels pressure to pretty up its bid.

Meanwhile, News Corp is still mulling a hand in the Yahoo deal, Reuters reported.

For coverage of Yahoo’s earning today, check Internetnews.com.