meets on "Header have_post problem"

Hi every one,

i am using have post in my header but when i go to my category it's showing only one category post on all category post . please any one help to me sort out this problem. i am using below code

<?php	

query_posts('showposts=2&cat=12');
if (have_posts()) :
$i=0;
while (have_posts()) : the_post();
?>

Thanks in advance.