var randomnumber=Math.floor(Math.random()*6)
switch (randomnumber)
{
case 1:
var headerimg="/by_capability/civilaviation/assets/category_civaviation.jpg"
  break;
case 2:
var headerimg="/by_capability/landforces/assets/category_landforces.jpg"
  break;
case 3:
var headerimg="/by_capability/militaryaviation/assets/category_milaviation.jpg"
  break;
case 4:
var headerimg="/by_capability/space/assets/category_space.jpg"
  break;
case 5:
var headerimg="/by_capability/marine/assets/category_marine.jpg"
  break;  
default:
var headerimg="/by_capability/militaryaviation/assets/category_milaviation.jpg"
}