Link to folder

Hello,

I use to be able to open a folder with my code below.  It opens the Railroad Plans folder and lists multiple PDF's.  It quit working and no gives me a Error 403 Forbidden.  It works great on my local c: drive??

<li><a href="Documents/Railroad Plans/" class="subtitles"><strong>Map Link</strong></a></li>

Any help is much appreciated/

Z