Setting up a Static IP Address?

I am trying to set up a Static IP address for a server. I have done this before, but had to reset my modem because I forgot the password for something (Not the password to get onto the router though, I was able to port forward).

So I have portforwarded everything, and as I am setting up the static IP address, I am in the Internet Protocol Version 4 (TCP/IPv4) properties and I tell it to use the following IP address. I put in my IP for the IP address, the Subnet mask automatically fills in, and the default gateway, which for me is 192.168.0.1. Then I go into the ipconfig/all in command prompt and type in the Preferred and Alternate DNS server IPs.

This is how I have it set up:

IP address: 192.168.0.150

Subnet mask: 255.255.255.0

Default Gateway: 192.168.0.1

Preferred DNS server: 72.240.13.7

Alternate DNS server:

I click Validate settings upon exit, and when I exit, I get a message;

"Warning - Multiple default gateways are intended to provide redundancy to a single network (such as an intranet or the Internet). They will not function properly when the gateways are on two separate, disjoint networks (such as one on your intranet and one on the Internet). Do you want to save this configuration?"

I have done this before, but it all got reset, so I am trying it again, and I do not have multiple gateways.

I have no idea what that means, and never had this problem before. What am I doing wrong and how can I fix it? I have tried ignoring it, but it just disconnects me from the internet until I run a diagnostics on it.