Printer ink confusion?

i have a HP photosmart 4400 and i need black and color ink. when i look at websites that sell it, they have numbers on them like 21, 95 etc..whats the difference? and for listings that show a certain cartridge is for the photosmart series it doesn't have my number. why is this? thanks so much.





(also, whats a good site to order cheap ink from?)Printer ink confusion?
The different numbers refer to different printers. The best I can figure is that as they go along, they make new printers that require different types of ink. It probably has something to do with the way the printer uses the ink. You have to read the instructions that came with your printer to figure out what type you need. You can't mix and match. The cheapest places to by ink are Target and Walmart. Amazon has good deals too. There's also the refill option at places like Walgreens (with color for $15 and black for $10) but I only do that in emergencies. When you do that, the printer won't tell you how much ink you have b/c it's not a new cartridge. Also, the quality's not as good but it's not a really noticeable diff.