function category_onclick(categoryId)  {
    document.getElementById("button").value = "ClickCategory";    
    document.getElementById("hidCategoryId").value = categoryId;

    if (categoryId != 0)  {
       categoryNav = new String(document.getElementById("hidCategoryNav").value);    
       categorySearch = new String("," + categoryId);
       found = false;

       if (categoryNav.indexOf("," + categoryId) >= 0)  {
          categoryNavStart = categoryNav.substring(0, categoryNav.indexOf(categorySearch) + categorySearch.length);
          categoryNavEnd = categoryNav.substring(categoryNav.indexOf(categorySearch) + categorySearch.length, categoryNav.length);

          document.getElementById("hidCategoryNav").value = categoryNavStart;

          found = true;
       }

       if (!found)  {
          if (document.getElementById("hidCategoryNav").value == "")  {
             document.getElementById("hidCategoryNav").value = "," + categoryId;
          } else  {
             document.getElementById("hidCategoryNav").value = document.getElementById("hidCategoryNav").value + "," + categoryId;
          }

       }
    } else  {
       document.getElementById("hidCategoryNav").value = "";
    }

    document.forms['IndexForm'].submit(); 
}