Moving sideways using gluLookAt(); C++

it helps some times To move sideways you simply have to translate the eye position along the camera's right vector.
To find the right vector, remember that the cross product of two vectors gives a perpendicular vector. So, the cross product of your forward vector and your up vector will give the right vector.

// find the Right vector. (forward cross product up)
float right[3];
right[0] = forward[1] * up[2] - forward[2] * up[1];
right[1] = forward[2] * up[0] - forward[0] * up[2];
right[2] = forward[0] * up[1] - forward[1] * up[0];

// now translate your eye position
[self setEye:[self eyeAtIndex:0] + right[0] * SPEED_MOVE atIndex:0];
[self setEye:[self eyeAtIndex:2] + right[2] * SPEED_MOVE atIndex:2];

With these it helps The answer by Nicol Bolas pretty much tells what you're doing wrong so I'll skip that. You are looking for an solution rather than telling you what is wrong, so let's step right into it.
This is code I use for projection matrix:

glViewport(0, 0, mySize.x, mySize.y);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(fovy, (float)mySize.x/(float)mySize.y, nearPlane, farPlane);

glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
gluLookAt(  camera.GetEye().x,camera.GetEye().y,camera.GetEye().z,
camera.GetLookAt().x,camera.GetLookAt().y,camera.GetLookAt().z,
camera.GetUp().x,camera.GetUp().y,camera.GetUp().z);

fixed the issue. Will look into that further After some tests, I found the problem: it's the scrollbarhead which is causing the problem. I think you've got this script from some website, and this table header is adding the gap you don't want.
I "removed" it with a simple display:none, and it's working (I also changed the width to 100%):