Each table row has an onclick method which alerts some information about the tr DOM node that you are clicking on.<br/><br/>
The offsetTop property is the distance, in pixels, between the top of the element (in this case, the row) and the top of the offsetParent (which should be the table).  Rows further down in the table should return a greater offsetTop value.<br/>


<table border="1">
  <tbody>
    <tr id="row-one" onclick="alert(this.id + ' ' + this + ' has an offsetTop of ' + this.offsetTop + ' where the offsetParent is ' + this.offsetParent)"><td>one</td>
    </tr>
    <tr id="row-two"  onclick="alert(this.id + ' ' + this + ' has an offsetTop of ' + this.offsetTop + ' where the offsetParent is ' + this.offsetParent)"><td>two</td>
    </tr>
    <tr id="row-three"  onclick="alert(this.id + ' ' + this + ' has an offsetTop of ' + this.offsetTop + ' where the offsetParent is ' + this.offsetParent)"><td>three</td>
    </tr>
    <tr id="row-four"  onclick="alert(this.id + ' ' + this + ' has an offsetTop of ' + this.offsetTop + ' where the offsetParent is ' + this.offsetParent)"><td>four</td>
    </tr>
    <tr id="row-five"  onclick="alert(this.id + ' ' + this + ' has an offsetTop of ' + this.offsetTop + ' where the offsetParent is ' + this.offsetParent)"><td>five</td>
    </tr>
    <tr id="row-six"  onclick="alert(this.id + ' ' + this + ' has an offsetTop of ' + this.offsetTop + ' where the offsetParent is ' + this.offsetParent)"><td>six</td>
    </tr>
  </tbody>
</table>