Looks good from what I can tell. Couple of things. First off, you probably shouldn't call randomize() at the beginning of each loop, you'll tend to get bad random numbers that way. Call it at the beginning of the program and never again.
Second, to make your life easier, consider using arrays to store the values of the different cards, thus getting rid of all of your if statements.
Instead of this:
Code:
if(ran==11)
{
display='J';
cardvalue=10;
}
if(ran==12)
{
display='Q';
cardvalue=10;
}
etc....
try this:
Code:
// declared at top
char cardnames[13]={'A','1','2','3','4','5','6','7','8','9','0','J','Q','K'};
int values[13]={1,2,3,4,5,6,7,8,9,10,10,10,10};
// used instead of the if statements
display=cardnames[ran-1];
cardvalue=values[ran-1];
And last 
you don't have aces being 1 OR 11 depending on which is better. Makes it hard to get a blackjack!
