Question: When I use different layouts to support different screens , should I use dp or px .

Answer: 
yes @levib answer is short and correct one to use. Another alternative is that you can use slideUp() and slideDown() functions.

```
$(".fold_reply").click(function() {

    if ($('.reply').css('display', 'none')) {
        $(".reply").slideDown("slow");
    }
    else {
        $(".reply").slideUp("fast");
    }

});​

```
```
$(".fold_reply").click(function() { 
     var style=$('.reply').css('display');
    if (style=='none') {
        $(".reply").show(500);
    }
    else {
        $(".reply").hide(500);
    }

});​

<input type="button" class='fold_reply' value="button">

<div class='reply'>
    text<br/>text<br/>text<br/>text<br/>text
</div>​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​

```

**[Working Demo](http://jsfiddle.net/DQvZT/)**