A simple snippet to detect placeholder support with jQuery on form inputs and fallback accordingly.

gistfile1.js

//Find if user browser supports placeholder
jQuery(function() {
  jQuery.support.placeholder = false;
	test = document.createElement('input');
	if('placeholder' in test) jQuery.support.placeholder = true;
});

if(!$.support.placeholder) {
	// If placeholder is not supported
	var inputPlaceholder= function () {
  	var input = $('form').find('input[placeholder]');

    input.each(function (index) {
      $(this).val($(this).attr('placeholder'));
    });

    input.on('focus', function () {
      if ($(this).val() == $(this).attr('placeholder')) {
        $(this).val('');
      };
    });

    input.on('blur', function () {
      if ($(this).val() == '') {
        $(this).val($(this).attr('placeholder'));
      };
    });
  }
    inputPlaceholder();
}