Can anyone help? Print size and quality of image

[mumof3]

Hi I am trying to order some prints for myself from photobox but if i go above size 6x4 then it says medium quality and any higher it can say poor quality and some of my picture maybe cut off
So if i want a photo that is 10x8 i cant risk it as it takes some of the pic away and says medium quality. So confused on sizes of images.I dont have a clue.

I take my photos with a DSLR Canon 450D i then edit them using Picnik at the mo as im saving for PS, sometimes i get a message whilst editing on picnik saying picture to big so i auto rezize it and thats it. Help please, really would appreciate it.Hope i make sence :/

Thank you xx

 

[johnsy]

Sounds like the images has been shrunk and are now of a low resolution. Try and re edit them in some different software using the full size images. That's if you still have them and have not saved over the originals?