Javascript: Select specific child of the current element using THIS

The HTML you have provided is invalid. When defining attributes, you have to give them a name. Let's assume you have this:

 <span class="data">data in here...</span>

With jQuery, you can simply do this without an inline event handler. In your $(document).ready() you could put:

$('.feeds').mouseover(function () {
    var $span=$('span.data', this);
});

$span will hold access to your span (in a jQuery collection).

jsFiddle Demo - jQuery version

If you need a Javascript only solution (with your inline event handler: onmouseover="select(this)"), you would go with something like this:

function select(me) {
    var span=me.getElementsByClassName('data')[0];
}

getElementsByClassName() is only available on modern browsers, but you can use a fallback as well for ancient IEs.

jsFiddle Demo - Plain Javascript / Inline handler

Note: If you have more than one .feeds, please consider using a class instead of an id for someDiv, because an id can only appear once in a HTML document.

Working example - http://jsfiddle.net/4NAJ9/1/

<script>
$(function(){
    $('.feeds').hover(function(){
        var data_span = $(this).find('.data');
        alert(data_span.html());
    }, function(){
        // If you wanted something to happen 'onmouseout', put it here
    });
});
</script>

<div class="feeds">
    <div id="someDiv"></div>
    <div class="moredivs"></div>
    <span class="data">data in here...</span>
</div>

If you're willing to use jQuery, then you really don't want to be adding an inline onclick event to each .feeds element.

It's better to keep your Javascript separate from your HTML - jQuery allows you to do this easily.

Somethink like this?

$('.feeds').mouseover(function() {
  $('span',this).html();
});