The housing marketing may not be back to normal just yet, but it is heading in that direction, according to a report from Zillow. Last year's soaring home price appreciation, frantic demand from investors, and increased negative equity are all expected to slow somewhat this year, according to the real estate company.On a national basis, home prices rose 6.4 percent year-over-year in the fourth quarter, but annual price gains are expected to decline to 4.8 percent by year's end."Below the surface of last year's market, a number of unsettling trends started to emerge as a result of rapid and ultimately unsustainable appreciation, setting up a bit of a mixed bag for 2014," said Stan Humphries, chief economist at Zillow.Some of the markets that had the highest price gains last year are already slowing, which according to Zillow, is "a welcome sign in markets that risk crossing over into bubble territory as rising mortgage interest rates create affordability issues for homebuyers."Markets like those in California and the Southwest that experienced accelerated appreciation last year may stall this year due to issues with affordability, leading to "volatility that could potentially cause whiplash for homebuyers and sellers," according to Zillow.Nationally, price appreciation is already slowing down, according to Zillow. After reaching a high of a 7.1 percent annual price gain in August, price gains remained below 7 percent for the entire fourth quarter.