A very common question people have is "Does wine go bad?" but the answer is not as simple as the question. It is dependent on what kind of wine it is and how it is stored. Fortified wines have about a months lifespan once open, whereas table wines last only about 3-5 days. On a positive note, an old wine doesn't harm you, it just doesn't taste as good.
Why does wine go bad? In short, acetic acid bacteria starts to consume the wine's alcohol then metabolizes which causes a vinegar like smell. Also, the alcohol can oxidize, which takes away the wine's freshness and gives it a nutty taste. Both of these chemical reactions can be slowed down by keeping the wine at a lower temperature.
Sparkling wine, like soda, loses it's carbonation quiet fast once opened. A wine stopper will help, but only prolongs the quality of the wine for 1-3 days when in the fridge. Because they have more bubbles, traditional sparkling wines such as Champagne, will last a little longer.
Sweet white and rose wines will get about 5-7 days in the fridge with a cork. The longer it's opened the less vibrant the fruit flavor and character of the wine will be. If the white wine is full-bodied, like a Chardonnay, it's life drops to about 3-5 days because they tend to oxidize faster due to being exposed to more oxygen during the aging process before bottling.
If a red wine is higher in tannin and acidity, it tends to last longer after opening than a red wine that has little tannin like a Pinot Noir. Reds should be stored in a dark, cool location like a chiller once opened, but if that's not available to you the refrigerator is the next best place. Red wines will last about 3-5 days with a cork.
Port, Sherry, and Marsala, along with other fortified wines, will last about a month with a cork if kept in a cool, dark place. The addition of Brandy to these wines gives them a longer life. A good fact to keep in mind is the sweeter the dessert wine, the longer life it has.
If you like to keep a box of wine the fridge you can count on it's life to be about 2-3 weeks for either red or white. This is because the bag inside of the box is an airless environment which keeps the wine longer. However, make sure to check the expiration date on the box because there are regulations on foods that are stored in plastic.