What did the 24th amendment to the constitution prohibit?

The 24th Amendment prohibited poll taxes or other taxes as qualifications for voting.

Poll taxes had been a way states had discriminated against black voters, by using their lower income status and poll taxes as a way to prevent them from going to the polls.  During the civil rights movement of the 1950s and 1960s, this was challenged.  The 24th Amendment, ratified in 1964, said: "The right of citizens of the United States to vote in any primary or other election for President or Vice President for electors for President or Vice President, or for Senator or Representative in Congress, shall not be denied or abridged by the United States or any State by reason of failure to pay any poll tax or other tax," and added:  "The Congress shall have power to enforce this article by appropriate legislation."