var min=8;
var max=18;

function ModifyFontSize(direction) {
      $('div.IssueContent').children().each(function() {
        ModifyThis($(this),direction);
        $(this).children().each(function() {
          ModifyThis($(this),direction);
          $(this).children().each(function() {
            ModifyThis($(this),direction);
            $(this).children().each(function() {
              ModifyThis($(this),direction);
              $(this).children().each(function() {
                ModifyThis($(this),direction);
                $(this).children().each(function() {
                  ModifyThis($(this),direction);
                  $(this).children().each(function() {
                    ModifyThis($(this),direction);
                  });
                });
              });
            });
          });
        });
     });

}

function ModifyThis(mit,direction) {
        var p=mit.css('fontSize');
        if (p) {
           var s = parseInt(p.replace("px",""));
        } else {
           var s = 12;
        }
        s =s+( direction=="-" ? -1 : 1);
        if(s>min && s<max) {
           mit.css('fontSize',s+"px");
        }
        
}