The image path requires a single or double forward slash and I have no control over when

I am currently programming PHP on a server. But when uploading images to my webspace and showing them I sometimes need

 myaddress.com//image.jpg 

      

        
        
        
      

    

and sometimes

 myaddress.com/image.jpg 

      

        
        
        
      

    

It seems to switch from time to time. Why is this and how can I fix it? I have two pages that are loaded with ajax directly when they are selected in the navigation bar. And when I use // it works on one of the pages and when I use single / it works on the other. Why?

Thanks in advance!