It's the digital camera industry's dirty secret: All pixels are not created equal. They don't tell you, because they want you to suffer from pixel envy. That's how they get you to buy the newest digital camera models.
But is a 10-megapixel camera really better than an 8-megapixel model? Or even a lowly 5-megapixel model? Not necessarily. Here's a case in point:
The 12-megapixel Nikon D300 retails for a little under $1,500. Nikon's D700 is also a 12-megapixel camera... but it sells for about $3,000. Since both are DSLR's, if you don't need the extra features on the D700, you'll get the same quality pictures for $1,500 less, right?
Wrong. Though both cameras offer roughly the same nominal resolution, at 23.6 x 15.8 mm, the D300's sensor is less than half the size of the D700's. That means each pixel in the D700 sensor is able to absorb more light... and thus can provide greater detail and richer color.
But don't knock the D300... it's sensor is still about twice the size of the average point-and-shoot camera's sensor.
Greater nominal resolutions can also create a disadvantage. Smaller pixels tend to increase "noise" - off-color or grainy spots in your photos. That's why your old 6-megapixel camera may have produced better looking photos than your new 10-megapixel model.
So when you're looking for a digital camera, look at two numbers: resolution ("megapixels") and sensor size. Because resolution alone is just half the story.