Beer: Off Smells and Flavours...

I came across the following on the homebrewtalk forum, and thought it worth posting here as a reference guide in case I need it.... 

If your beer smells like… The term is…. The source may be….

Adhesive bandages (phenolic) 

Bacterial contamination; residue from a sanitizing agent ( this odor is expected of certain style beers)

Apple cider (Acetaldehyde)

Refined sugar in the recipe or bacterial contamination

Baby diapers (Enteric) 

Bacterial contamination

Banana (Banana esters) 

Certain ale yeast strains, particularly Bavarian Weizenbier and Belgium Strong Ales 

Barnyard (Enteric) 

Bacteria contamination

Bubblegum (Bubblegum) 

Certain Ale yeast strains, particularly Belgium Strong Ales and Bavarian Weizenbier 

Butter/Butterscotch (Diacetyl) 

Bacteria, certain yeast strains, warm fermentation, short aging

Cardboard or paper (Oxidized) 

Contact with air; old, stale beer

Cauliflower or cooked cabbage (Vegetal) 

Bacteria contamination

Cloves (Phenolic) 

Certain yeast strains; such as those in Bavarian Weizenbier

Cooked corn (DMS (dimethyl sulfide)) 

Poor grain quality; bacterial contamination

Cooking sherry (Oxidized) 

Contact with air; long and warm fermentation 

Green Apple (Acetaldehyde) 

Refined sugar in the recipe; bacterial contamination

Leather (Oxidized) 

Contact with air and/or old, stale beer

Marker (Phenolic) 

Bacterial contamination; residue of sanitizing agent

Matches (burnt) or Sulfur (Hydrogen sulfide) 

Natural by product of fermentation that’s normally flushed out with the production of carbon diaoxide

Mold (Moldy) 

Sanitation problem; leeking package seal

Nail polish remover (Solvent like) 

Esters produced during high temperature fermentation

Olives (green or black) or Pickles (Acetic) 

Acetobacteria contamination

Paint thinner (Solvent like) 

Fusel alcohols produced during high temperature fermentation

Rotten eggs (Hydrogen sulfide) 

Yeast autolysis 

Rubber (Hydrogen sulfide)

Yeast autolysis 

Skunk (Light struck) 

Damage from light

Smoke (Phenolic) 

Use of dark or smoked grains that evoke this aroma

Soap (Soapy) 

Residue from sanitizing agents

Vinyl upholstery (Phenolic) 

Bacterial contamination; residue from sanitizing agents

Wet dog (Musty) 

Bacterial contamination; lengthy aging of bottle conditioned beer

If you beer tastes odd 

Blood (Metallic) 

Iron in water supply 

Butter/butterscotch (Diacetyl) 

Certain yeast strains, warm fermentation

Chalk (Astringent) 

Overfermentation; misuse of grain

Harsh (Astringent)

High hop bitterness; misuse of grain

Powdery (Astringent) 

Lack of sweetness; grain astringency 

Salt (Salty) 

Use of brewing salts especially sodium chloride and magnesium sulfate

Sour milk (Lactic) 

Lactic fermentation (which is intentional in some beer styles such as Berliner Weisse)

Tin can (Metallic) 

Iron in water supply; contact with metals