Smarty problem with onload JS function

[GS VISION]

I have a div which I want to show only once on every 24h to every visitor so I wrote a code with cookies but I can`t call it in the body section of header.tpl with onload function.I recieve the following error:

Fatal error: Smarty error: [in /home/laptopia/public_html/themes/laptopia/header.tpl line 46]: syntax error: unrecognized tag: document.getElementById('bgtop').style.visibility = 'hidden' (Smarty_Compiler.class.php, line 446) in /home/laptopia/public_html/tools/smarty/Smarty.class.php on line 1095

Thanks in advance!