problem with modifing headers?

I want to put 2 lines of code required by this statitsic tool :
https://webanalyse.sourceforge.net/
These 2 lines of code are the very first thing that should be in the page. When I put these lines in the WP template before everything else I get an error message that looks like this :
Warning: Cannot modify header information – headers already sent by (output started at /home/somebaud/www/static/wallpapers.php:1) in /home/somebaud/www/webanalyse/include/stats_main.inc on line 72
Is there something preventing WP user from modifying header informations?
many thanks in advance
B.