Navigation button(s) are hidden below the images

Question:

Some of my navigation buttons are hidden below the images of my Navigation menu. 

Answer:

You should have a  <!DOCTYPE> tag on the top of your HTML page. Please, add the following attribute: "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"

This attribute is used when the requirements of the XHTML 1.0 are not strictly followed.

 
In addition, the issue could be caused because the z-index element of the navigation buttons in your CSS is less than some other elements. You will need to increase that z-index element in your CSS.