A Special Real Estate Exemption for Capital Gains
Since 1997, up to $250,000 in capital gains ($500,000 for a married couple) on the sale of a home is exempt from taxation if you meet the following criteria
You have lived in the home as your principal residence for two out of the last five years.
You have not sold or exchanged another home during the two years preceding the sale.
Also note that as of 2003, you may also qualify for this exemption if you meet what the IRS calls "unforeseen circumstances" such as job loss, divorce, or family medical emergency.