You would have to do something like this:
PHP Code:
if (isset($_GET['id'])) {
$result = mysql_query("SELECT * FROM members WHERE name = '%s'", mysql_real_escape_string($_GET['id']));
if (mysql_num_rows($result) > 0) {
// use result to display member info
} else {
// error or no user in database
}
} else {
// list members
}
Something like that.
Google for some articles on using query strings in your URL using the GET method, and using them to display the info you want.