Different systematicists have categorized the red panda (Ailurus fulgens) in a number of different ways. Originally, they were placed in the Family Procyonidae - due to morphological similarities between the red panda and the raccoons. Although raccoons are restricted to North and South America, and the red panda is strictly Asian in distribution.
Sometime in the late 80's/early 90's, genetic work done with giant pandas, red pandas, bears and raccoons suggested that red pandas and giant pandas were definitely related, giant pandas were somewhat genetically similar to bears, and the other relationships were unclear or even contradictory. Based on these findings, some workers put both panda species into the Family Ursidae. Some put them in their own seperate family, the Ailuropodidae. Others put the red panda into the Procyonidae, and the giant panda into the Ursidae, and tried to figure out what that meant when the two (obviously) closely related pandas were put into separate families.
More recently, more work has been done resolving these similarities and differences, and red pandas have been broken out into their own Family, the Ailuridae. Some put the giant pandas into that family as well, some keep the giant pandas in Ailuropodidae, and some put the giant pandas in Ursidae.
See? Clear as mud.