<p>I am cloning a hidden table row then populating it and after validation I want to show the row using a jquery effect ... say .show("slow")</p>

<pre><code>var baseRow = $("#tasks tr#baseTaskLine");
var newRow = baseRow.clone();
var lastRow = $("#tasks tr[id^='TaskLine_']" + dayClass + ":last");

var newRowId;
if (lastRow.length == 0) {
   newRowId = "TaskLine_new0";
}
else {
   newRowId = "TaskLine_new" + lastRow[0].rowIndex;
}

newRow.attr("id", newRowId);

:
[populate new row]
:

if (lastRow.length == 0) {
   baseRow.after(newRow);
}
else {
   lastRow.after(newRow);
}
newRow.hide();
:

:
[validate via webservice call]
:
newRow.show("slow");
</code></pre>

<p>This does show the row but it appears instantly. I have tried hiding all the <code>&lt;td&gt;</code> elements of the row then showing those and that does seem to work but some strange styles get added to each <code>&lt;td&gt;</code> which interfere with the formatting i.e. <code>style="display: block;"</code></p>

This is not going to work this way. Table rows and cells are not meant to be displayed as blocks so the show/fade effects are not going to work on table rows directly.
You could, however, put a <div> in each of the cells, something like this:
```
```
<table>
<tr id="row1"><td><div>Cell1:1</div></td><td><div>Cell2:1</div></td></tr>
<tr id="row2"><td><div>Cell1:2</div></td><td><div>Cell2:2</div></td></tr>
</table>
```
```
and then to the following:
```
```
$('#row2 td div').show('slow');
```
```
This will yield the expected behaviour.