Grove Serial LCD Problem

I bought Grove serial lcd but I cant work it I always get this error “SerialLCD slcd(11,12);”

here is a sample :

/*

SerialLCD Library - Hello World

Demonstrates the use a 16x2 LCD SerialLCD driver from Seeedstudio.

This sketch prints “Hello, Seeeduino!” to the LCD

and shows the time.

Library originally added 16 Dec. 2010

by Jimbo.we

http://www.seeedstudio.com

*/

// include the library code:

#include <SerialLCD.h>

#include <NewSoftSerial.h> //this is a must

// initialize the library

SerialLCD slcd(11,12);//this is a must, assign soft serial pins

void setup() {

// set up

slcd.begin();

// Print a message to the LCD.

slcd.print(“hello, world!”);

}

void loop() {

// set the cursor to column 0, line 1

// (note: line 1 is the second row, since counting begins with 0):

slcd.setCursor(0, 1);

// print the number of seconds since reset:

slcd.print(millis()/1000,DEC);

}

I download library and search internet but I cant do that.

can u help me please?