Custom header does not display in web browser

I am new to Raipweaver and web building in general so that is why I decided to get Rapidweaver. I have found the right code to change the header image in my ‘Split’ theme and it works fine in Preview mode but it does not display in the web browser once it is published or exported. I have made sure that the filename matches the code and the image is in the right place in my resources.