The problem is that after navigating back, the items found will expire. Therefore, we need to update the code to update the elements after going back.
Update the code below:
WebDriver driver = new FirefoxDriver();
driver.manage().timeouts().implicitlyWait(20, TimeUnit.SECONDS);
driver.manage().window().maximize();
driver.get("http://www.adspapa.com/");
WebElement catBox = driver.findElement(By.xpath("html/body/table[1]/tbody/tr/td/table/tbody/tr/td[1]/table"));
List<WebElement> catValues = catBox.findElements(By.tagName("a"));
for(int i=0;i<catValues.size();i++)
{
catValues.get(i).click();
System.out.println(driver.getTitle());
driver.navigate().back();
catBox = driver.findElement(By.xpath("html/body/table[1]/tbody/tr/td/table/tbody/tr/td[1]/table"));
catValues = catBox.findElements(By.tagName("a"));
}
driver.quit();
I tested the above code at my end and its working tone. You can improve the code above according to your use.