Yes, Tetanus Toxoid does contain Thimerosal (mercury), in most vaccines. For more info: http://www.vaccinesafety.edu/thi-table.htm BUT, there are several tetanus vaccines that are free of mercury....
Tetanus toxoid is what a tetanus vaccine contains. You're body will make anti-bodies to tetanus once given the tetanus vaccine, offering you protection for "up to" 10 years from the bacterial disease...
The best answer I have found relating to the "difference" between toxoid and anti serum or anti toxin revolves more around the reason for application. While both may give the same result, the reason...