In this series, we take a look at the 25 stocks on the S&P 500 Index (SPX) that have turned in the worst performance during the past decade -- what went wrong, and what happens next.

First Horizon National Corporation (NYSE: FHN) operates as the holding company for First Tennessee Bank, making it one of many regional banks on our roster. If you're the intelligent, discerning audience that I assume you to be, I probably need only mention that FHN is in the mortgage-lending business for you to guess what might be ailing the stock.

What went wrong? At number 15 on our list of SPX laggards, FHN shed 76% of its value during the 10-year period ending June 30, 2008. The stock peaked at $48.65 in March 2004, but didn't start to plunge in earnest until July 2007. Say it with me, people: subprime.

While the share price didn't plummet immediately in response, FHN first revealed mortgage-related weakness in August 2006. The bank warned that quarterly earnings would be dented by deteriorating mortgage-market conditions, and profits fell during the next two quarters. FHN cited "lower gain on sale margins, further reductions in new mortgages and increased costs to hedge the servicing risks for mortgage loans" for the earnings weakness.

On September 4, 2007, FHN's head of employee services got chatty with The Memphis Daily News. John Daniel admitted that the bank was trimming its headcount gradually in a cost-cutting effort, but reassured the paper that the subprime crisis didn't have too deep an impact. "We don't see any significant reductions in staff as a result of what's happening in the mortgage industry right now," he asserted. Just a week later, on September 13, the Daily News reported that FHN was slashing 50% of its mortgage sales force, about 2,000 total positions.