is there a difference if using a slash in the query string?

Question

My webpage acts totally different if I use a slash before the ? in the URL. (example.com/?p=1 instead of example.com?p=1 ignores the stylesheet for some reason) is there a difference in the variable that my script gets using the GET method? And how do I make it so that it makes no difference if I use a slash or not? this is some of my code

    if (isset($_GET['p'])) {
    $page = round ((int) mysql_real_escape_string($_GET["p"]));
    if ($page > $tp or $page < 1) {
    $page = 1;
    goto a;
    }
    else goto a;
    }
    else $page = 1;