Start page parts
Bootstrap 3: split page in four equal parts : http://stackoverflow.com/questions/27825814/bootstrap-3-split-page-in-four-equal-parts
four equal part: http://www.bootply.com/qmwjea4pG3
How to “stick” a button over an image when re-sizing : http://stackoverflow.com/questions/35647044/boostrap-how-to-stick-a-button-over-an-image-when-re-sizing