Without any code, it is very hard to suggest anything. This gap might be there, because you have a twoside document and \flushbuttom is active. You could sove that using \raggedbuttom. Or there is another reason. Please provide a minimal working example to get more detailed help.
– Johannes_BApr 02 '15 at 11:06
\flushbuttomis active. You could sove that using\raggedbuttom. Or there is another reason. Please provide a minimal working example to get more detailed help. – Johannes_B Apr 02 '15 at 11:06