There are several problems with this sample code;
1) $Image = Imagecreate(200,200); should be
$Image = ImageCreate(200,200);
2) Imagepng=($image); should be
Imagepng ($Image);
Now this will create an image 200 X 200 with no content whatsoever.. to create some color include the following;
$background_color = ImageColorAllocate ($Image, 55, 55, 55);
So we have the revised sample code;
<?php
header ("Content-type: image/png");
$Image= ImageCreate(200,200);
$background_color = ImageColorAllocate ($Image, 255, 255, 255);
Imagepng ($Image);
?>
This script should be called from an img tag in an html page, eg. <img src="image.php">
If this does not solve your problem it may be that libgd is not properly configured or installed.