Problem:

The ab command can correct your common typos in vi automatically.

Resolution:

Vi  can be initialized by a list of initializations in a file called .exrc  located in your home directory.  

.exrc holds map, set and ab commands

The file is read by vi and ex on startup.  The ab command takes the form of

ab [abbreviation] [expansion]

This can be used to correct typos on the fly by using

ab  [typo]  [correction]

For example:

ab teh the

ab preform perform

.exrc can be created by vi.  Add your mappings and abbreviations to this file as you find you need them.