The Anarchy of King Stephen
Multiclassing is allowed between any of the base classes, advanced classes and prestige classes, with some caveats. A character who wishes to take a level in a given class must meet all prerequisites for that class.
When determining whether or not a character meets prerequisites, any Talents that duplicate Feats count as those Feats for sake of determining prerequisites.
For purposes of meeting prerequisites, a character’s Ranks in a skill are equal to his skill base (1/2 Hit Dice) + the skill’s Tier.
Non-humans may not take levels in the human base classes. However, a non-human may take a level in an advanced class so long as he meets the prerequisites for that class.
XP Penalties and Favored classes
There are no favored classes or XP penalties. Characters are free to multiclass as they see fit.