Thanks for this web

How to Find the URL of a File

http://support.hostgator.com/articles/how-to-find-the-url-of-a-file

 

this mention maindomain subdomain

http://www.inmotionhosting.com/support/website/getting-started-guides/where-to-upload-files

 

the key pointot me is,

if your site is     www.yourdomain.com

 

and the file in your host filepath is xxx/yyy/public_html/somefolder1/targethtml

 

then the valid href hyperlink to this file is

 

www.yourdomain.com/somefolder1/targethtml

 

for short, omit the word before public_html/