what is Hucks reaction to the footprints, and what could the reader infer about the future plot of the story using his reaction as evidence? what are some other superstitions that Huck and Jim believe?

The footprints stop before reaching the house, therefore Huck knew someone had been there and was just watching. Huck also recognized the "cross in the left boot-heel made with big nails, to keep off the devil." We can infer that Huck knows the owner of the boots, and that he's worried enough about this person to take all of his money to the Judge and ask him to invest it or keep it safe.

An entire blog devoted to their superstitions can be linked below;

http://blogs.setonhill.edu/JenniferHaun/005420.html