Forward searching refers to making a DVI viewer display a given document at a given location from within Vim. At present, this functionality is supported for YAP on windows and xdvi on *nix machines. Pressing \ls from within Vim should make the DVI viewer display the portion of the document where your cursor is placed.
Most DVI viewers need "source-special" information in order to do forward (and inverse) searching. This information is embedded in the dvi file if the LaTeX source is compiled with the --src-specials option. By default, Latex-Suite does not supply this argument to the compiler. See the section on g:Tex_CompileRule_dvi to find out how this option can be set.