A little late to the discussion but wanted to add 2 cents.
An appropriate rabbit diet depends not only on age and weight, but also the rabbit's purpose. Rabbits that are going to be bred have different nutritional needs than, say, indoor rabbits that are fixed. This is why one is going to find such contradictory advice on "proper" diet.
Someone mentioned corn, though, and I wanted to point out that the hulls of individual corn kernels are indigestible to rabbits. They can cause a fatal gut impaction. I've seen the x-rays of this.
That said, one will always find concerning any rabbit diet the "... yeah, but I've always fed _____ and my rabbit is just fine." There are always exceptions. [I knew of a 5 year old rabbit that had been housed indoors and was fed nothing but dry dog food!!]
I've had indoor, fixed pet rabbits for 30 years and have seen the diet recommendations for such rabbits be adjusted over the years as science learns more. The House Rabbit Society (referred to by cluckcluck) is for fixed, primarily indoor, pet rabbits -- not for breeding rabbits. Their recommendation for adult rabbits daily is unlimited grass hay, 2-4 cups of daily greens, and severely limited plain pellets (about 1/4 cup for a 5-7 lb rabbit). Treats like fruit (or carrot since they are high in sugar) should be limited to no more than 1-2 tbsp per day.
Most rabbits living in the wild don't have access to vegetables, of course there's no pellets either in the fields either. I personally have read it isn't a good thing, but like keeping all critters there is all kinds of different information out there. Do what you are comfortable with. I was just sharing what I thought and how I keep mine. 
