Redmine

<% content_for :header_tags do %>

  <script type="text/javascript">

	var timer;

	function validateInputfield(id,regexp){

		var regexp = new RegExp(regexp); 

		if(regexp.test($(id).val())){

			$(id).removeClass('invalid').addClass('valid');

			return true;

		}

		else{

			$(id).removeClass('valid').addClass('invalid');

			return false;

		}

	};

	$('#settings_host_name').live("keypress", function(){

		clearTimeout(timer);

		timer  = setTimeout(function(){

			validateInputfield('#settings_host_name','^[^0-9\:\./]+(([^/:@])||(:[0-9]+))+$');

		},500);

	});

	$(document).ready(function(){

		validateInputfield('#settings_host_name','^[^0-9\:\./]+(([^/:@])||(:[0-9]+))+$');

	});

  </script>

<% end %>

input.valid, input.invalid{padding-left:25px !important}

input.valid{background:#fff url("../images/true.png") no-repeat 2px 50%}

input.invalid{background:#fff url("../images/false.png") no-repeat 2px 50%}