Why can't I get anything to display with this code?

#include <iostream>
#include "GL/glfw.h"
#ifndef MAIN
#define MAIN
#include "GL/gl.h"
#include "GL/glu.h"
#endif
using namespace std;

void display();

int main()
{
    int running = GL_TRUE;
    glfwInit();

    if( !glfwOpenWindow( 640,480, 0,0,0,0,0,0, GLFW_WINDOW ) )
    {
        glfwTerminate();
        return 0;
    }

    while( running )
    {
        //GL Code here
        display();

        glfwSwapBuffers();
        // Check if ESC key was pressed or window was closed
        running = !glfwGetKey( GLFW_KEY_ESC ) &&
        glfwGetWindowParam( GLFW_OPENED );
    }

    glfwTerminate();

    return 0;
}

void display()
{
    glClearColor(0, 0,0, 0.0f);
    glClear(GL_COLOR_BUFFER_BIT);
    glLoadIdentity();
    gluLookAt(0, 0, 5, 0.0, 0.0, 0.0, 0, 1, 0);
    glScalef(1.0f, 1.0f, 1.0f);
    glTranslatef(0, 0, -2);
            glBegin(GL_POLYGON);
            glColor3f(1.0, 0.2, 0.2);
            glVertex3f(0.25, 0.25, 0.0);
            glVertex3f(0.75, 0.25, 0.0);
            glVertex3f(0.75, 0.75, 0.0);
            glVertex3f(0.25, 0.75, 0.0);
    glEnd();
    glFlush();
}