how to revert default Mac Apache install to original
Has another Apache been installed? From a terminal (Applications-&gt; Utilities-&gt; Terminal.app) try:

ps ax | grep httpd

You should see something like the following if your local web sharing is enabled:

25829   ??  Ss     0:00.04 /usr/sbin/httpd -D FOREGROUND -D WEBSHARING_ON
25831   ??  S      0:00.00 /usr/sbin/httpd -D FOREGROUND -D WEBSHARING_ON

Then try

ps ax | grep apache

This should return nothing if you are using the default install, but might if another server was installed.
If apache is running from anything other than /usr/sbin, then you may want to investigate your PATH environment variable in case it has been altered.
You could also try using the default httpd.conf file supplied by Apple (in case yours has been edited).

Make a backup of the current one

sudo cp /etc/apache2/httpd.conf /etc/apache2/httpd.conf.bak


Copy the 'original' httpd.conf file

sudo cp /etc/apache2/original/httpd.conf /etc/apache2/httpd.conf


Restart the web server

sudo apachectl restart



On a side note.. If you are or will be doing any long term web development, I would advise installing apache2, php, mysql, etc from MacPorts or Homebrew. There is a little bit of a learning curve, but it's easy when you get the hang of it and you will benefit over the long haul. Example port commands:
Search for applications to install

port search apache2

Install apache2

sudo port install apache2 (currently version 2.2.22)

Uninstall apache2

sudo port uninstall apache2

Upgrade..

sudo port upgrade apache2

Also, MacPorts installs everything into the /opt/ directory (I think Homebrew does as well), so you can always just delete the entire directory if you do not want them anymore. Again, if you do not mind digging in the trenches a bit and can be patient while your computer compiles these apps from source code (this can be lengthy), it will be worth your while.