function check_fields( field_object, alert_field_id, numeric_field )
{

	var alert_str = '';
	var str = field_object.value;


	if ( str.match( /[^a-z0-9 ]+/i ) )
	{
		str = field_object.value.replace( /[^a-z0-9 ]+/i, '' );

		if ( numeric_field )
		{
			alert_str = '<br><font color="red">Field must consist only of lowercase letters and/or digits!</font>';
		} else {
			alert_str = '<br><font color="red">Field must consist only of lowercase letters!</font>';
		}
	}
	document.getElementById( alert_field_id ).innerHTML = alert_str;

	if ( str != field_object.value )
	{
		document.getElementById(field_object.id).value=str;
	}

}



function check_field_length( field_object, min_length, alert_field_id, field_id )
{

	if ( field_object.value.length < min_length )
	{
		document.getElementById( alert_field_id ).innerHTML = '<br><font color="red">Username must be at least '+ min_length +' chars!</font>';
		setTimeout( 'document.getElementById( "'+ field_id +'").focus();', 100 );
	} else {
		document.getElementById( alert_field_id ).innerHTML = '';
	}

}


function check_birthdate_field( field_object, alert_field_id )
{

	var str = field_object.value;
	var date_fields = new Array();
	var current_date = new Date();

	if ( str.match(/\-/) )
	{
		if ( date_fields = str.split(/\-/) )
		{

			str = '';
			if ( typeof(date_fields[0]) != 'undefined' && date_fields[0] != '' )
			{
				if (date_fields[0] < 1900 || (date_fields[0] > current_date.getFullYear() - 18) )
				{
					alert_str = 'Please give a valid birth date!';
				} else {
					str = date_fields[0] + '-';
				}
			}

			if ( typeof(date_fields[1]) != 'undefined' && date_fields[1] != '' )
			{

				if ( date_fields[1].length < 2 )
				{
					str += date_fields[1];
				} else {

					if (date_fields[1] < 1 || date_fields[1] > 12 )
					{
						alert_str = 'Please give a valid birth date!';
					} else {
						str += date_fields[1] + '-';
					}

				}

			}

			if (typeof(date_fields[2]) != 'undefined' && date_fields[2] != '' )
			{
				if ( date_fields[2].length < 2 )
				{
					str += date_fields[2];
				} else {

					if (date_fields[2] < 1 || date_fields[2] > 31 )
					{
						alert_str = 'Please give a valid birth date!';
					} else {
						str += date_fields[2];
					}

				}
			}

		}

	}

	return str;

}


function check_site_url( field_object )
{
	if ( field_object.value == '' )
	{
		document.getElementById(field_object.id).value = 'http://';
	} else {
		if ( ! field_object.value.match(/^http:\/\//) )
		{
			document.getElementById(field_object.id).value = 'http://' + field_object.value;
		}
	}
}