osama@osama-laptop:~/Desktop/fontforge$ sudo apt-get install libX11-devPassword:
Sorry, try again.
Password:
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following packages were automatically installed and are no longer required:
  libuninameslist0
Use 'apt-get autoremove' to remove them.
The following extra packages will be installed:
  libx11-dev libxau-dev libxdmcp-dev x11proto-core-dev x11proto-input-dev
  x11proto-kb-dev xtrans-dev
The following NEW packages will be installed:
  libx11-dev libxau-dev libxdmcp-dev x11proto-core-dev x11proto-input-dev
  x11proto-kb-dev xtrans-dev
0 upgraded, 7 newly installed, 0 to remove and 0 not upgraded.
Need to get 8754kB/8918kB of archives.
After unpacking 22.4MB of additional disk space will be used.
Do you want to continue [Y/n]? y
Get:1 http://archive.ubuntu.com feisty/main xtrans-dev 1.0.3-1 [69.2kB]
Get:2 http://archive.ubuntu.com feisty/main libx11-dev 2:1.1.1-1ubuntu3 [8685kB]