By Marla Brill

Karin Prangley, a 33-year-old Chicago estate planning attorney, attempted to guess her father-in-law's password to gain access to his business computer after he suffered a debilitating stroke several years ago at age 62. None of them worked.

"At the time he owned a building supply company, and he ran most of the business through his Yahoo e-mail account," Prangley says. "But he hadn't left his password with anyone, so the family had no way of accessing the contents. We didn't know which orders had been filled, what was coming in, who the business owed money to, or who to bill."

Yahoo would only provide the password with a court order. "As an attorney, I knew that takes at least a month," Prangley says. "The business couldn't wait that long." With important records sealed off, the business lost a significant amount of money and eventually closed.

Computer passwords, increasingly the portals to our financial and personal lives, can be sealed in a digital tomb once their owners pass on, or are seriously ill. With no record of them, family and loved ones may be shut out from information in bank accounts and financial data, or sentimental assets like family photographs and music collections.

"Going through someone's things used to mean sorting through paper statements and watching the mail for bills to come in," says Minneapolis estate planning attorney James Lamm. "Now, that information is often located on a computer. If families can't access it, it can create a lot of headaches."

Indeed, such headaches may get more prevalent as a growing population of older Americans go paperless. About 57 percent of bank customers age 55 and above prefer banking online, compared with 20 percent a year earlier, according to a 2011 survey by the American Banker's Association. And the increasing online savvy of senior Americans extends to social media and photo-sharing web sites.

Lamm says several of his clients have been locked out of password-protected computers after a loved one has died, sometimes necessitating desperate measures.

"On one occasion, we had to hire a computer forensics expert to get into the hard drive," he says. "It delayed settlement for several weeks and created a lot of stress for the family during what was already a very difficult time."

Policies for how to handle access requests differ widely among service providers.

According to a Yahoo! spokesperson, the firm's policy "is to treat their e-mail and the content of their messages as confidential." If family members or representatives contact the customer care department, the firm will shut down a deceased user's account.

Google requires documentation, such as a death certificate, and an order from a U.S. court, before allowing access to a deceased user's e-mail by an authorized representative. Facebook's less restrictive policy allows immediate family members or executors to delete an account with acceptable documentation, such as a death certificate.

To avoid complications and make sure everything is accounted for, John Romano, co-author of "Your Digital Afterlife," advises that you write an inventory of your financial, professional and sentimentally valuable online assets, including user names and passwords associated with them. These should be kept somewhere secure, like a home safe or bank safe deposit box, and at least one other person should know where it is.

There are web-based services, too, such as Entrustet and LegacyLocker, which permit users to store information about their online assets and have it released to authorized individuals. While they're easier to update than a written list that's squirreled away somewhere, most of them are fairly new, and it's possible they may not be around many years from now.

As a simpler solution, Lamm suggests keeping a written master password in a secure, physical location, which will open up a digital property list stored on a computer or other electronic device.

His own estate plan's master password is stored in a secure vault in his office. Through this master password, Lamm's authorized representatives and family members will be able to open up a digital asset list he created with a software program called LastPass. Because it syncs with all his electronic devices, including his iPad, iPhone, personal computer and laptop, he only needs to input updates once. The information is encrypted, for an extra layer of security.

Regardless of how you record your digital "keys," experts say anything is better than hoping your relatives will guess that the name of a late, beloved cat, is also your password.

"The important thing is not to assume people know everything that's inside your head," Lamm says.

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