welcome aboard!
if you pitch yeast on the higher end of the fermentation temp for ale yeast, it will lend more fruity, estery flavors, as opposed to the lower temps. maybe even a stronger alcohol after-taste. fermenting on the lower end will provide a little cleaner, better flavor, and probably help the yeast have a better, active ferment (which is what we all want). depending on the brand of yeast you use (liquide White Labs or Wyeast), they will have a temp range on the vial or pack. or, you can check the web pages of each (
www.whitelabs.com, don't know Wyeast's). White Labs has a FAQ's page that you can get some good info off of too.
if your not using liquide yeast, i recommend a good quiality liquide yeast (and a starter if possible, but not required) like White Labs or Wyeast. that is one of the biggest improvements you can make on your homebrew.
hope this helps.
cheers!
DeRoux's Broux