Why is yahoo stock the worst performing stock today?

The market goes through phases. One day, society loves a company, and the next day, they hate that company. The day after, society finds a worse company, and it likes the first company more. Maybe not as much as they did two days earlier, but more than they did the day before. Then, company number one upgrades, and society likes company number one more than they did on day one. It's just the way the market works. Unfortunately for some companies, those companies never rebound, and they end up going out of business. It could be due to inflation, underperformance, or the people just don't like the product.

Yahoo is up 1.23% today, not down. It's up about 33% in the past year. Personally I would not own it, I don't think Marissa Mayer is all she is touted to be as a CEO and I don't think the company is well positioned for the future.

The worst performing? Not even close. Yahoo is up as I write this and at it's lowest point it was only down 0.7%. Many stocks are doing worse.

Stocks go up and down all the time. Sometimes for no apparent reason. Tech stocks frequently move with the sector. Tech is down, so Yahoo is actually going against the trend.

Should you buy it? I don't follow it closely so can't offer an opinion on that.

YHOO is UP about a percentage point so far today, what on Earth are you talking about?

http://finance.yahoo.com/echarts?s=YHOO+Interactiv...

It's also basically flat over the last year, and has more than DOUBLED over the two years;

http://finance.yahoo.com/echarts?s=YHOO+Interactiv...