Code:
 
// Three integers printing middle interger numberically: 1/14/2008, 2:05PM

//

#include <iostream> // allows program to output data to the screen
#include "Rhod_2a.h"
using std::cout; // program uses cout
using std::cin; // program uses cin
using std::endl; // program uses endl

// function main begins program execution
int main()
{
	int number1; // first integer to compare
	int number2; // second integer to compare
	int number3; // third integer to compare

	cout << "Enter three integers: "; //prompt user for data
	cin >> number1 >> number2 >> number3; // read three integers from user

	if ( number1 <= number2 )
	cout << number1 << if (number2 < number1 )
		cout << number2 << if ( number3 < number1 )
			cout << number3 << endl;
	if ( number1 > number2 )
		cout << number1 << if ( number2 > number1 )
			cout << number 2 << if ( number2 < number3 )
				cout << number2 << if ( number3 <= number2 )
					cout << number3 << endl;
	if ( number1 > number2 )
		cout << number1 << if ( number1 > number3 )
			cout << number1 << if ( number2 > number1 )
				cout << number2 << if ( number2 > number3 )
					cout << number2 << if ( number3 > number1 )
						cout << number3 <<  if ( number3 > number2 )
							cout << number3 << endl;
	return 0; // indicate that program ended successfully
} //end function main
This is what it would look like if you indented properly.
And Visual Studio indents for you, so why not just accept the default indentation it uses instead of making a mess of everything?
As I can see, there's plenty of errors. It's illegal to output an if! Not to mention the program doesn't make sense.