I downloaded and installed Ubuntu 17.04 I wanted to try it out. I've used Fedora for a few years. The wired setting look about the same as Fedora's it says I'm connected at 1000mbs but the web browser won't connect to the web. The MTU is set on automatic I tried 1500 but it still won't connect.
Any ideas to try. I have a 1000mbs router and a 1000mbs lan card. I tried the on board internet but it won't work either.
The router is connected to a cable company modem. I leave the router on all the time. I use cat 6 cable for connections.
I also can't log into the terminal as a superuser.

The reason you can't log on as root is that Ubuntu locks the root account. Just log on as the first user you created and you will find that you have sudo rights to all commands.

A few possible troubleshooting tricks:
1) Can you ping the router?
2) Can you ping 8.8.8.8?
3) What does dmesg say about your network card? (it will be right at the end of the boot messages)
4) What happens if you run ip link show?

I can ping the ip address.
I can ping 8.8.8.8
I can ping the ipv4 ip address.
It can't locate the router.
It loads so fast I didn't have time to read the messages.
I'm may have a static ip as it's been the same for quit a while even though I upgraded my cable modem to a higher speed.
Thanks for your help.

You router is likely at ip address xxx.xxx.xxx.001. That's the normal situation. You can use a traceroute to identify your router also. It would normally be the first hop. See man traceroute for more.

You can determine your computer's ip address with either of these commands:

ip is the newer of the two. Some distros include both; some include just one.

I got it to say the internet was working but the firefox wouldn't connect. I downloaded linux mint and installed it to try I was wasteing to much time on Ubuntu. It had the internet working as it was installing.

Glad you got it working. I consider Mint a very nice job of work.

Was this a wired or wireless connection?

Just for curiosity, what is the make/model of the computer?

This is a wired connection. It's one I put an Asus mother board and Athlon 4 core processor with both onboard and a network card in I had windows 7 installed and Microsoft doesn't like the fact that I only used it occasionally. They got bad pushing windows 10 and I got a bad download from them and they couldn't update the registration number.
I paid $69 for them to repair it took them about 20 hours of tech time. I could have erased the hard drive and reinstalled quicker. I got a nasty call that windows had expired and I had to pay more money. They put a program to reconnect and disable the mouse. I used a usb floppy drive with a floppy that stamps zero's on the hard drive.
I had went in safe mode and tried to find the problem but was unable. I have another computer with 8.3 as I have a few items I require it for.
I use fedora 26 95% of the time. But I'm going to try Mint.
I think Ubuntu was confused because I have both onboard and a network card. It had a habit of disconnecting and looking for the onboard network.

did you try powering off and on your cable modem?

I have in the past but not this time.

I developed the same problem in my Fedora 26 computer. I called the cable company I rebooted both my cable modem and my router. I still had a problem and I connected directly to my network card from the cable modem. I called back and he said I had a couple of channels out. If I brought cable modem he would exchange I did this and the woman who ports the numbers left a 3:30 but could do it later in the evening she works part time. He put the modem on a test stand and it worked fine. He said he would have a crew to check the connection at 8:30AM on Monday.I hooked it up and installed another router. It pulls 30mbps I should have 50mbps. Hopefully I can get full speed Monday.