There is a couple of ways to do this.
1. Add to the location array in a php file. For example add
PHP Code:
$location[] = array("Login");
This will be assigned as the $location variable you see in the Smarty Template.
2. If you know what the $main assigned Smarty variable is for a specific page you can add something like this to the <title></title> section.
HTML Code:
{if $main eq "Login"} ---code--- {/if}
Then what you have as “---code---“ will only show on the Login screen.