function isURL(url) {
 return url.match(/^(ht|f)tps?:\/\/[a-z0-9-\.]+\.[a-z]{2,4}\/?([^\s<>\#%"\,\{\}\\|\\\^\[\]`]+)?$/);
}

function isEmail(email) {
	var filter = /^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$/;
	if (!filter.test(email)) return false;
	return true;
}

function isUsername(username)
{
 if (/[^a-z0-9\_\-]/i.test(username) || username.length<6 || username.length>25 || username.indexOf(' ')!=-1) return false;
 return true;
}


function isEmpty(str)
{
  new_str=str.replace(/\s/g,"");
  if(new_str.length==0) return true;
  return false;
}