web page and Admin mumbled

OK I own a web site called: www.matrixnutrition.net I noticed in the last few weeks that my web pages have been compromised with some writing on it;

Warning: session_start(): Cannot send session cookie - headers already sent by (output started at /home/content/m/a/t/matrixnu/html/matrix/information.php:8) in /home/content/m/a/t/matrixnu/html/matrix/includes/functions/sessions.php on line 93

Warning: session_start(): Cannot send session cache limiter - headers already sent (output started at /home/content/m/a/t/matrixnu/html/matrix/information.php:8) in /home/content/m/a/t/matrixnu/html/matrix/includes/functions/sessions.php on line 93

I finaly decided to go to my admin home page which alows me to maintanance my site and see if there was some way to fix this or whatever. I was then shocked, because not only was my maintanace site not there anylonger, but also more scribble in replacement;
Warning: session_start(): Cannot send session cookie - headers already sent by (output started at /home/content/m/a/t/matrixnu/html/matrix/admin/includes/application_top.php:8) in /home/content/m/a/t/matrixnu/html/matrix/admin/includes/functions/sessions.php on line 73

Warning: session_start(): Cannot send session cache limiter - headers already sent (output started at /home/content/m/a/t/matrixnu/html/matrix/admin/includes/application_top.php:8) in /home/content/m/a/t/matrixnu/html/matrix/admin/includes/functions/sessions.php on line 73

Warning: Cannot modify header information - headers already sent by (output started at /home/content/m/a/t/matrixnu/html/matrix/admin/includes/application_top.php:8) in /home/content/m/a/t/matrixnu/html/matrix/admin/includes/functions/general.php on line 128

Does anyone know what this is and how I can regain my control? The original web master who built this site is no longer available and I'm at a loss in whgat to do..
Thanks...

 

my antivirus reports that your site has been known as an attack site, you might have to check with your host and they can point you to where it's been compromised.

 

When confronting my host (Godaddy.com) they mention of my password of that site in which they host was weak and someone was able to compromise it.
Went on their site (godaddy) and changed it to a more secure one, so I hope.

They also mention that I go and clean the site up, yeah ok! so how do you do that? I would love to get rid of those creeps in there.

Then they said after its all done, contact Google and inform them that my site is now clean and to take off the WARNING! plastered all over the net...

Ok then Godaddy ask for me if I have a backup disc of my site and send them the material so they can upload new clean files. I have a disc of which the web designer said for me to download after it was complete, as I did, but when I try to look at it on my computer, it looks like some pic's and I see no script of any kind, lots of black spaces and as mentioned pics from my original site.

Another question I have is, how the heck am I going to get my control panel of my Admin. account so I can make changes to the site? For whom ever the creeps were removed and replaced with some form of scripting.. (see below)

Need more help here guys... thx


From the admin control page
Warning: session_start(): Cannot send session cookie - headers already sent by (output started at /home/content/m/a/t/matrixnu/html/matrix/admin/includes/application_top.php:8) in /home/content/m/a/t/matrixnu/html/matrix/admin/includes/functions/sessions.php on line 73

Warning: session_start(): Cannot send session cache limiter - headers already sent (output started at /home/content/m/a/t/matrixnu/html/matrix/admin/includes/application_top.php:8) in /home/content/m/a/t/matrixnu/html/matrix/admin/includes/functions/sessions.php on line 73

Warning: Cannot modify header information - headers already sent by (output started at /home/content/m/a/t/matrixnu/html/matrix/admin/includes/application_top.php:8) in /home/content/m/a/t/matrixnu/html/matrix/admin/includes/functions/general.php on line 128