NEW YORK – A volatile week on Wall Street drew heavy traffic to financial Web sites, as investors hastened to check their portfolios or move money around in what was dubbed the worst financial meltdown since the Great Depression.

Online brokerage Scottrade Inc. saw its highest-volume trading day ever on Thursday. The two previous days were also among the eight busiest Scottrade has ever had, spokeswoman Kelly Doria said, and overall, orders were up 60 percent from the same week last year. She said the service suffered no loss of availability.

Some online trading sites saw a slowdown from all the activity. In some cases Thursday, the sites were performing as much as 12 times slower than normal, according to Keynote Systems Inc., a San Mateo, Calif.-based company that measures Web site performance.

The company did not specify which sites performed the slowest, though it cited online brokerage E-Trade Financial Corp. as one that held up well.

In some cases, trading sites' performance slowdowns meant they were operating at only 95 percent availability – meaning 5 percent of users couldn't complete what they wanted to do.

The week has been extremely volatile, beginning with massive losses Monday as investors woke up to two storied financial firms gone in a buyout and a bankruptcy. There was a rebound Tuesday, another plunge Wednesday and rallies on Thursday and Friday.

Charles Schwab Corp., the nation's largest discount brokerage, “definitely saw higher-than-usual traffic this week,” said spokeswoman Sarah Bulgatz in an e-mail. But she added that efforts to add capacity “seemed to have paid off” – with the exception of “some minor issues” at the market open Friday due to very heavy volume. These issues have since been resolved, she added.

At investment management company Vanguard Group, online activity was busy Thursday, about what the company sees during tax season, said spokeswoman Rebecca Cohen. She said investors log on to the site to check their accounts “any time there is volatility” in the markets.

Hitwise, an Internet traffic-monitoring service, said visits to online broker-dealers and financial news Web sites like Yahoo Finance have up been by about a third this week, with attention steadily increasing as the week progressed.

The financial turmoil didn't appear to be causing online versions of runs on banks. Keynote's index of banking sites – which include JPMorgan Chase & Co., Citibank as well as troubled Washington Mutual Inc. – did not show any significant issues or slowdowns, said Shawn White, Keynote's director of external operations.

AP Technology Writer Jordan Robertson and Business Writer Eileen AJ Connelly contributed to this report.