Wired or wireless Internet. BTW - You didn't delete the internet, you just messed up the connection. Tell us the whole story. it'll be easier to help.

If wireless, we need to know the hardware your using.
lspci if internal
lsusb if plug in

You've been here before, you know the routine.

BTW - Nice to see you again.

Ok, it sounds like you deleted the connection from Network Manager. Since I do not use network manager we can wait for someone who is more experienced with the app to assist.

Do you have a network icon anywhere on your panel? If networking is down it might have a red "x" over it. If not, you should be able to search you menu for "network connections" or "network manager".
If you do have an icon on the panel, you can left click on it and look for a check box with "Enable Networking", make sure it's checked. If it wasn't, fixing your problem may be a simple as that.
If you don't see an icon, look in the menu for Network Connections, click on wired, then click on the eth0 and then edit, and make sure the box is checked next to "Connect Automatically" and "System Connection".

If it's a wireless connection, check the boxes in Network Connections under Wireless".

I'm hoping someone with an Ubuntu install can check what I've just written. I use KDE on Fedora, and, while Network Manager is similar on both Gnome and KDE, there might be differences that they can point out.

Yes, Tom is right in those procedures. What I want to know is are you wired or wireless? You did not state that. I don't think you deleted the connection, just disconnected. All you should really do is click on the "networkmanager" on the panel, select "auto etho" if you are wired or select the wireless connection.

First, instead of guessing, how were you connected? Lets hope, you did not uninstall the "networkmanager" app.