function getParameter ( queryString, parameterName ) {   
	// Add "=" to the parameter name (i.e. parameterName=value)   
	var parameterName = parameterName + "=";   
	if ( queryString.length > 0 ) {      
		// Find the beginning of the string      
		begin = queryString.indexOf ( parameterName );      
		// If the parameter name is not found, skip it, otherwise return the value      
		if ( begin != -1 ) {         
			// Add the length (integer) to the beginning         
			begin += parameterName.length;         
			// Multiple parameters are separated by the "&" sign         
			end = queryString.indexOf ( "&" , begin );      
			if ( end == -1 ) {         
				end = queryString.length      
			}      
			// Return the string      
			return unescape ( queryString.substring ( begin, end ) );   
		}   
		// Return "null" if no parameter has been found   
		return "null";   
	}
}