The problem is that there is a typographic error in your installation command. Specifically, you have told apt-get to try to install a package called libcur14-gnutls-dev. But the correct name is libcurl4-gnutls-dev.

That is, you have an l (i.e., a lower-case L) where you should have a 1 (a numeral one). It is (semantically) "lib curl 4," not "lib cur 14".

So run this instead:

sudo apt-get install libcurl4-gnutls-dev

(Also, when installing packages on the command-line, it's advisable to run sudo apt-get update first, unless you have done so recently.)

However, you might not want to install Git this way at all.

The instructions you're following appear to be for compiling Git yourself. That's a perfectly valid thing to do, but for most people it's a lot of unnecessary work, plus if you do that, the system will not be able to upgrade Git automatically when a newer version is available. (It may also, in some ways, have trouble integrating with the installed Git, because the package manager won't "know" it is installed.)'

Therefore, as Tarun suggested, you may just want to install Git directly (Ubuntu has Git packages, which is way faster and simpler!).

sudo apt-get install git-core

Typically you only need to build Git from source yourself if you need a version newer than the version available for Ubuntu. Even in those situations, there are often alternatives, so feel free to let us know more about what you need.