So your css files are located in the Main_Template_files folder in the root of your website?

and you can see them when you enter?

http://www.yourwebsite.com/Main_Template_files/aldolex.css

dec_obrien

THese are the three files linked in the head section of the page (which is a master page):

Is the webpage located in the root of the website or inside a folder?

 Next look in the rendered HTML when opening the page. if your webpage is inside the root, is the href attribute

href="Main_Template_files/Aldolex.css"

Or when it is located in a folder

href="../Main_Template_files/Aldolex.css"