Unable to locate an element in Selenium (htmlUnitDriver)

I am unable to locate an element in selenium, which i used htmlUnitDriver. well driver is working fine but I'm unable to find google search text box element.

Here is the code:

import java.util.concurrent.TimeUnit;
import org.openqa.selenium.By;
import org.openqa.selenium.WebElement;
import org.openqa.selenium.htmlunit.HtmlUnitDriver;

public class SampleUnitDriver 
{
    public static void main(String[] args) throws Exception 
    {

            HtmlUnitDriver unitDriver = new HtmlUnitDriver();
            unitDriver.manage().timeouts().implicitlyWait(10, TimeUnit.SECONDS);
            unitDriver.get("http://google.com");
            System.out.println("Title of the page is -> " + unitDriver.getTitle());

            WebElement searchBox = unitDriver.findElement(By.xpath(".//*[@id='gs_htif0']"));
            searchBox.sendKeys("Selenium");
            WebElement button = unitDriver.findElement(By.name("gbqfba"));
            button.click();
            System.out.println("Title of the page is -> " + unitDriver.getTitle());


    }
}

Here is an Error:

Exception in thread "main" org.openqa.selenium.NoSuchElementException: Unable to locate a node using .//*[@id='gs_htif0'] For documentation on this error, please visit: http://seleniumhq.org/exceptions/no_such_element.html Build info: version: '2.53.0', revision: '35ae25b1534ae328c771e0856c93e187490ca824', time: '2016-03-15 10:43:46' System info: host: 'user-PC', ip: '192.168.1.52', os.name: 'Windows 7', os.arch: 'amd64', os.version: '6.1', java.version: '1.8.0_51' Driver info: driver.version: SampleUnitDriver at org.openqa.selenium.htmlunit.HtmlUnitDriver.findElementByXPath(HtmlUnitDriver.java:1165) at org.openqa.selenium.By$ByXPath.findElement(By.java:361) at org.openqa.selenium.htmlunit.HtmlUnitDriver$5.call(HtmlUnitDriver.java:1725) at org.openqa.selenium.htmlunit.HtmlUnitDriver$5.call(HtmlUnitDriver.java:1721) at org.openqa.selenium.htmlunit.HtmlUnitDriver.implicitlyWaitFor(HtmlUnitDriver.java:1367) at org.openqa.selenium.htmlunit.HtmlUnitDriver.findElement(HtmlUnitDriver.java:1721) at org.openqa.selenium.htmlunit.HtmlUnitDriver.findElement(HtmlUnitDriver.java:606) at com.digitalmqc.automation.action.SampleUnitDriver.main(SampleUnitDriver.java:19)

Any help can be appreciated.

You are locating wrong element, You should try as below :-

HtmlUnitDriver unitDriver = new HtmlUnitDriver();

unitDriver.manage().timeouts().implicitlyWait(10, TimeUnit.SECONDS);
unitDriver.get("http://google.com");
System.out.println("Title of the page is -> " + unitDriver.getTitle());

WebElement searchBox = unitDriver.findElement(By.name("q"))
searchBox.sendKeys("Selenium");
WebElement button = unitDriver.findElement(By.name("btnG"));
button.click();
System.out.println("Title of the page is -> " + unitDriver.getTitle());

Hope it helps..:)