The most common cause of this problem is not being on top of how you organise and reference files on the webserver. The fact that the html displays means that the location of the html is configured correctly. So now you need to reference the image relative to wherever you configured the document root on your webserver. For example, if the images are in a lower directory than the html you need to refer to them relative to where the html is stored. If the html and images are in subdirectories of the same location then you need to refer up and down a directory. Just trace where it is and configure accordingly.