Help with query

[tubedogg]

What's the error you are getting?

Two notes just off the top...you should be taking into account the TABLE_PREFIX, like shown below, and you don't need single quotes around an integer such as the joindate, so the query would look like:
$newmembers = $DB_site->query_first("SELECT COUNT(*) AS count FROM ".TABLE_PREFIX."user WHERE joindate > ".(time()-3600*24).");