How to navigate a subframe inside a frameset using Selenium WebDriver?

I need to get the result from the table "td". But before I can do that I need to navigate a frame that contains it. The frame is one of the frameset elements that belongs to the mainFrame. I tried to use all types of navigating the "child" subframe non of which works:

 driver.switchTo().defaultContent();
    Thread.sleep(1000);
     driver.switchTo().frame("mainFrame.0.fr_resultsNav~ResultsMaxGroupTemplate0.9766101221774707");
    driver.switchTo().frame("main.Frame.1.fr_resultsNav~ResultsMaxGroupTemplate0.8811790466176727");

// even: driver.switchTo().frame("mainFrame.0.fs_main");

The following is the brief layout of the webpage:

<frame src="banner.asp" name="topFrame" scrolling="no" noresize="noresize" id="topFrame" title="topFrame">

<frame src="" name="mainFrame" id="mainFrame" title="mainFrame" wd_frame_id_="5f4c10bc7e0960070bfda831655b8b0c">

    <frameset id="fs_main" border="0" frameborder="no" framespacing="0" rows="70,87,*">
.....................

        <frameset id="fs_content" cols="23%,*" framespacing="0" frameborder="no">
.....................
            <frameset cols="*,9" id="LeftFrameSet" framespacing="0" frameborder="no">
.....................
            <frame frameborder="0" name="fr_classification~ResultsMaxGroupTemplate0.609021034867735" title="Results Classification Frame" id="fr_classification~ResultsMaxGroupTemplate0.609021034867735" src="/lnacui2api/results/shared/waitMessage.do?wmibIdRand=61_T16938265013_rand_1363544453847" scrolling="Auto" onload="paintResultsBorder('ResultsMaxGroupTemplate0.609021034867735');">

....................

<form name="results_listview_ResultsListForm" method="post" action="/lnacui2api/results/listview/listview.do" id="results_listview_ResultsListForm">

..........

<td nowrap="" height="20"> <span id="new">&nbsp;All Results</span> (294)</td>
</form>

....................

Do I need to navigate the frameset before I can navigate a subframe? I read the documentation. All internet examples give a simple sample code: driver.switchTo().frame("mainFrame.0.child"). It does not work in this case. Please, take a look at the above script.

I agree, you cannot directly switch to a child frame. Also, make sure to switch to the defaultContent (driver.switchTo.defaultContent) every time you want to switch frame. With regard to your example, driver.switchTo().frame("mainFrame.0.child") --- this could also work, but you need to get rid of unnecessary quotation marks.

Find the index of main frame starting from zero then use

driver.switchTo.frame(mainFrameindex);

Then find the index of sub frame in the main frame

driver.switchTo.frame(subFrameIndex);

You cannot directly switch to a child frame without first switching to the parent frame. This is how it works.