A basic error:

"The name of a kerning class must start with an underscore (e.g. _a)."

and

"Each kerning class and each metrics class must have exactly one key glyph defined –this is done by following one of the glyph names in the glyph definition by the quotesingle (') character. The key glyph acts as a “representative” of the class."

http://www.fontlab.ch/downloads/manuals/FLS5WinManual.zip

PS If you use a .fea file/format, it should be something like this:

@_a = [ a aacute ];

NB the double space after the "a".

The line should read...

@_a = [ a  aacute ];

...but HTML collapses extra space characters unless they're escaped (as in  ) or inside of a <pre> element.