Virtual Photo Exhibition with Bootstrap ( error - solved )

Project:   Virtual Photo Exhibition

Programming language:     HTML,  CSS,   Javascript 

Front end framework:     Boostrap

.

I linked CSS-CDN and 

Javascript-CDN in index.html.  

I made another file for pictures

This img src didn't work in result.

It shows only word "falls" without picture.

After many attempts, it finally worked with these codes.