Browser keeps asking to d/l png file

[Anon]

I have a php file that generates an image, I have this header at the top of the code.

Header( "Content-type: image/png");

When i load the php file, the browser keeps asking me to open the .png file or download the file, I just want the browser to display the image upon load like it used to. I'm not sure what i changed but the browser used to just display the image on loading the php file. Is there a setting somewhere I have to change?

thanks