Is it really important to take vitamin d and calcium supplement together? what if you do not is it serious? but i take vitamin c and vitamin d together is this okay?

Vitamins combined in: all foods, beware lots of untrue promotions. If vitamin D3 (crucial to enable both calcium absorption from food & the bone forming cells to form bone; + other issues) concentrations are upper normal, e.g.70-80 ng/ml, then rarely even need Ca beyond within food. ↑ vitamin C rarely of any value for people living in 1st world countries; Lookup: "Linus Pauling & Vit. C"; actual evidence using Google.