CSS selector is not finding element in selenium grid -

i trying find submit element. html structure below.

<div>    <span class="combutton"><a href="javascript:void(0);">submit</a></span> </div>  <div>   <span class="combutton"><a href="#cancel">cancel</a></span> </div>  

in browser using firebug tried

$('div .combutton')[0].click() 

which clicks on submit perfectly. using selenium driver element not found. please tell me how using

driver.findelement(by.css("cssselectorstring")) 

what did in firebug shouldn't have effect since it's clicking on span , not a inside it.

this should work, unless omitted parts of markup otherwise prevent it:

driver.findelement(by.cssselector("div:first-child .combutton a")).click();