What am i missing or doing wrong?

ok, im just trying to open an opengl window and make a triangle appear. this code is based on a tutorial i found. what am i missing or doing wrong?

Code:

#include <GL\glut.h>


void Display(void)
{
	glClear(GL_COLOR_BUFFER_BIT);
	glLoadIdentity();
	glBegin(GL_POLYGON);
		glColor3f(0.0,0.0,0.0);
		glVertex3f(-0.5,-0.5,-3.0);
		glColor3f(1.0,0.0,0.0);
		glVertex3f(0.5,-0.5,-3.0);
		glColor3f(0.0,0.0,1.0);
		glVertex3f(0.5,0.5,-3.0);
	glEnd();
	glFlush();			
}

void Reshape(int x, int y)
{
	if (y == 0 || x == 0) return;  
	glMatrixMode(GL_PROJECTION);  
	glLoadIdentity();
	gluPerspective(40.0,(GLdouble)x/(GLdouble)y,0.5,20.0);
	glMatrixMode(GL_MODELVIEW);
	glViewport(0,0,x,y);  
}

int main (int argc, char **argv)
{
	
	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_SINGLE);
	glutInitWindowSize(300,300);
	glutCreateWindow("Intro");
	glClearColor(0.0,0.0,0.0,0.0);
	glutDisplayFunc(Display);
	glutReshapeFunc(Reshape);
	glutMainLoop();
	return 0;
}

Try here:

http://cboard.cprogramming.com/game-programming/