It will take 24 hours for data to start showing in your Google Analytics pages but you could also check that your ID is in the right format for the site. It should look like:
UA-XXXXXX-X
You can find it if you look under 'Profile Settings' and then look in the top corner and click 'Check Status'. You will see your ID next to 'Web Property ID'.
You will also be shown some example Javascript. The ID you need will also be shown there and will look like either
_uacct = "UA-XXXXXX-X";
or
var pageTracker = _gat._getTracker("UA-XXXXXX-X");
UA-XXXXXX-X
You can find it if you look under 'Profile Settings' and then look in the top corner and click 'Check Status'. You will see your ID next to 'Web Property ID'.
You will also be shown some example Javascript. The ID you need will also be shown there and will look like either
_uacct = "UA-XXXXXX-X";
or
var pageTracker = _gat._getTracker("UA-XXXXXX-X");