Need Opinion - Language Redirection Script...

Hi... I wasn't there for some time but now I need opinion... I hope someone would be able to say something about my script... what should be fixed, what I can do to improve it...

it is universal language redirection script for few pages that I work on and I need it to be as good as it can be... would this be working in every browser in which scripts like that can work? If now what I should add?

(why I aded "en" and "en-US"? The script first checks if there is exact name and then it converts it to small letters and takes only two first... just in case someone would ask before finishing read...)

 <script TYPE="text/javascript"> 	 languages=new Array("pl", "en", "en-US"); 	 default_language="en"; 	 if (navigator.language)    navigator_language=navigator.language 	 else if (navigator.browserLanguage)    navigator_language=navigator.browserLanguage 	 else if (navigator.systemLanguage)    navigator_language=navigator.systemLanguage 	 else if (navigator.userLanguage)    navigator_language=navigator.userLanguage 	 else if (window.navigator.language)    navigator_language=window.navigator.language 	 else    navigator_language=default_language; 	 in_list=-1; 	 for (i=0; i<languages.length; i++)    if (languages[i]==navigator_language)   	 in_list=i; 	 if (in_list>=0)    language=navigator_language 	 else    navigator_language=navigator_language.substr(0,2).toLowerCase(); 	 for (i=0; i<languages.length; i++)    if (languages[i]==navigator_language)   	 in_list=i; 	 if (in_list>=0)    language=navigator_language 	 else    language=default_language; 	 open_site="./"+language+"/index.html"; 	 window.location.replace(open_site);  </script>