This article is pretty accurate and I appreciate the list of foods not to feed. A correction I would make is the statement that veggies are a majority of a guinea pig’s diet. Actually the majority of their diet should be grass hay, such as Timothy or Orchard, and hay should be available at all times. I would be concerned about a new owner limiting hay after reading the section about overfeeding. Guinea pigs stuff themselves with hay but that doesn’t cause them to get overweight.
I agree with ItsaZoo; overall an accurate article and helpful for newbies! The only things I'd like to add to what ItsaZoo said are these:
~ With citrus fruits, oranges are ok! Yes, they're acidic, and too much can cause tummy upset, and too large of pieces can cause a sore mouth. But small pieces as treats are perfectly ok.
~ Kale and spinach are also ok, but though they're high in vitamin c, which is good, they're also extremely high in calcium, which is bad. Too much calcium can cause bladder stones and kidney stones. Some guinea pigs rarely or never have issues with excess calcium, but others--- like one of my own guinea pigs--- will start getting calcium powder/ grit in their urine even if they get only a small amount of a high calcium food.
~ And as was already pointed out, hay is crucial to a guinea pig's diet and they should have an unlimited amount every day. Hay keeps not only their digestive track healthy, but also their teeth.
~ Piggies should have around 1 cup of veggies every day, avoiding any excess of fruits/veggies/greens that are high in sugar, calcium, vitamin A, or oxalates.
Other than that the article is helpful pointing out other dangers, specifically human foods!