I installed Apache2 but when I type http://localhost/ in browser it show an error "Unable to connect".

I figured what i did i deleted "default" file in /etc/apache2/sites-enabled/
Can somebody who have apache installed post me his content of that file?

You should repair the file from your package manager. What distro are you running?

sudo apt-get install --reinstall apache2
commented: solved +6

Another problem I deleted the original index.html and put my own, after few hours i deleted second index.html but when i type http://localhost/ in my browser i displays file which i deleted.

Another problem I deleted the original index.html and put my own, after few hours i deleted second index.html but when i type http://localhost/ in my browser i displays file which i deleted.

I solved that i just cleared my history in firefox.

Did you get everything working again? If so please mark this thread as solved, if not then post back here with your issues. Good luck!