1) that notice of the sale was not proper,
2) the terms of the sale were unconscionable,
3) the sale was conducted fraudulently or
4) that justice was otherwise not done.
If it is found to be invalid, it simply voids the sale, and both parties are back in the same position they were before the sale. This means that the lender will still have its order of foreclosure, and it will just attempt another sale.