Lighttpd

Hi !
I have problems with firefox and lighttpd !
When i make an empty directory with index.html in it and start like
http://myhost.com/ firefox is trying to download the index.html file as binary file
I dont have problems with other browsers , only with firefox
I dont have problems with http://myhost.com/index.html only when i try to reach http://myhost.com/
Here is my configuration :

 server.document-root = "/usr/local/lhttpd/htdocs" 
 server.port = 80
 server.pid-file = "/usr/local/lhttpd/logs/lighttpd.pid" 
 server.max-request-size = 4096
 server.name = "85.187.1.206" 
 server.errorlog = "/usr/local/lhttpd/logs/error.log" 
 server.tag = "Security-BG.Org HTTPD" 
 server.dir-listing  = "enable" 
 #server.event-handler = "syspoll" 
 server.modules = ( "mod_auth", "mod_access", "mod_status", "mod_fastcgi", "mod_accesslog" , "mod_rewrite", "mod_rrdtool")
 server.max-keep-alive-requests = 100
 server.max-keep-alive-idle = 32
 server.stat-cache-engine = "fam" 
 index-file.names = ( "index.php", "index.html", "index.htm" )
 accesslog.filename = "/usr/local/lhttpd/logs/access.log" 
 rrdtool.binary = "/usr/local/bin/rrdtool" 
 rrdtool.db-name = "/usr/local/lhttpd/htdocs/httpd.rrd" 
mimetype.assign = (
".rpm" => "application/x-rpm",
".pdf" => "application/pdf",
".sig" => "application/pgp-signature",
".spl" => "application/futuresplash",
".class" => "application/octet-stream",
".ps" => "application/postscript",
".torrent" => "application/x-bittorrent",
".dvi" => "application/x-dvi",
".gz" => "application/x-gzip",
".pac" => "application/x-ns-proxy-autoconfig",
".swf" => "application/x-shockwave-flash",
".tar.gz" => "application/x-tgz",
".tgz" => "application/x-tgz",
".tar" => "application/x-tar",
".zip" => "application/zip",
".mp3" => "audio/mpeg",
".m3u" => "audio/x-mpegurl",
".wma" => "audio/x-ms-wma",
".wax" => "audio/x-ms-wax",
".ogg" => "audio/x-wav",
".wav" => "audio/x-wav",
".gif" => "image/gif",
".jpg" => "image/jpeg",
".jpeg" => "image/jpeg",
".png" => "image/png",
".xbm" => "image/x-xbitmap",
".xpm" => "image/x-xpixmap",
".xwd" => "image/x-xwindowdump",
".css" => "text/css",
".html" => "text/html",
".htm" => "text/html",
".js" => "text/javascript",
".asc" => "text/plain",
".c" => "text/plain",
".conf" => "text/plain",
".text" => "text/plain",
".txt" => "text/plain",
".dtd" => "text/xml",
".xml" => "text/xml",
".mpeg" => "video/mpeg",
".mpg" => "video/mpeg",
".mov" => "video/quicktime",
".qt" => "video/quicktime",
".avi" => "video/x-msvideo",
".asf" => "video/x-ms-asf",
".asx" => "video/x-ms-asf",
".wmv" => "video/x-ms-wmv",
".bz2" => "application/x-bzip",
".tbz" => "application/x-bzip-compressed-tar",
".tar.bz2" => "application/x-bzip-compressed-tar" 
)

-- root