Is my wine CORKED?
This is the most common wine fault (well, not with stelvin caps, just wines with corks in them) Trichloranisole or TCA can make a wine smell musty and mouldy. There will be no fruit on the nose at all when a wine is corked.
Help! There is mould on top of my cork! - Don't worry, that is probably a bit of ullage, it shouldn't affect the wine. If you have pieces of cork floating in the wine, don't stress, its probably just a sign that you opened the bottle incorrectly!
If your wine has a bit of a vinegery, it may not be corked, it might just have some Volatile Acidity. VA is a bacteria in wine that causes the formation of acetic acid — the acid that gives vinegar its characteristic flavor and aroma.
Oxidation: - Wine is too old.
Does your wine have a bit of a sherry smell? Does it taste a bit dull? Not fruity at all? Is the wine more brown in colour than red? Is it more brown than white? Its potentially oxidation. Has the bottle been opened for a few days? Air contact spoils wine. This also occurs when a wine is simply too old.
Clear Crystals in your bottle?
This is "Tartaric Acid Crystals" known as Tartrates. They aren't harmful. Tartrates are a natural component of grapes and when wine becomes too cold or too old, crystals will form. This is a sign that a wine hasn't been over-treated during vinification.
My Wine is Cloudy or Fizzy
Cloudiness usually indicates the growth of yeast or bacteria; fizziness that the wine has undergone an unintentional second fermentation in its bottle. Both of these are definitely faults, often due to bad winemaking. It is likely the wine will be unpleasant, albeit harmless, to drink.
Hope this is helpful! Now go forth and drink good wine!