在firefox中运行Selenium Webdriver时，发现错误？“元素内的偏移无法滚动到视图中”以及“ HTMLSpanElement”

Question

@Test   
public void searchandSelectProduct() throws Exception
{       
 Actions action = new Actions(driver);
 WebElement mainMenu = driver.findElement(By.xpath("                     
 (//li[@id='categories']/a/span)[2]"));  
 action.moveToElement(mainMenu).moveToElement(driver.findElement
 (By.xpath("//li[@id='categories']/ul/li[10]/a/span")))
 .click().build().perform();    
 WebDriverWait wait = new WebDriverWait(driver, 10);
  element = wait.until(ExpectedConditions.elementToBeClickable(By.id("kAdd to 
  cart")));
  element.click();
 }

我已经使用HTML SPAN元素来标识该元素。谁能帮助我找出如何在不使用span作为元素的情况下运行此代码。