Medical information for 20,000 patients of a Stanford Hospital in Palo Alto, California, was accidentally posted online — and left up for more than a year. The detailed spreadsheet was found by a patient on a website called Student of Fortune, which helps students with schoolwork for pay. A spokesman for the hospital said the spreadsheet first appeared on the site as an attachment to a question about how to convert data into a bar graph. The spreadsheet contained names, diagnosis codes, account numbers, admission and discharge dates, and billing charges. The Department of Health and Human Services found that medical data for more than 11 million people have been improperly exposed in the last two years.