Invalid request while accessing website through public IP

[MonttY]

Hello, I am using Windows Server 2012 R2 and IIS to host my website. On LAN it works fine without any issue(I can connect from any computer through private ip), but when I try to access the website through my public IP, I get blank page with "Invalid request" in left corner. I have opened port 80 on my router and directed it to machine running the server.
For example here it says that Port 80 is open.
I have static IP.
No matter what I do this is what I get:

What could be the issue?

Thanks for help.

 

[kanewolf]

If this is a firefox browser, I would recommend you turn on some of the tools under the "Web Developer" in the tools menu. Start with the Web Console and see if you get any insight.