<input type="text" id="threadAbout" value="" class="postDescrFl" size="60" maxlength="50" />
<img src="http://s3.ucoz.net/img/fr/ic1/thread.gif" alt="" class="selectedImg" />
<img src="/images/threadIcons/image1.png" alt="Image1" />
...
<img src="/images/threadIcons/imageN.png" alt="ImageN" />
<div style="display:none">$_THREAD_DESCR$</div>

<div class="gDivLeft"><div class="gDivRight">
<table border="0" width="100%" cellspacing="1" cellpadding="0" class="gTable" id="frM53">
<tr id="frM54"><td colspan="2" class="gTableTop" id="frM55"><div style="float:right" class="gTopCornerRight"></div><a name="post">$FORM_TITLE$</a></td></tr>
<?if($ERROR$)?>
<tr id="frM1"><td colspan="2" align="center" class="gTableError" id="frM2">$ERROR$</td></tr>
<?endif?>
<?if($_USER$)?>
<tr id="frM3"><td class="gTableLeft" id="frM4">Name:</td><td class="gTableRight" id="frM5">$_USER$</td></tr>
<?endif?>
<?if($_THREAD_NAME$)?>
<tr id="frM25"><td class="gTableLeft" id="frM26">Thread name:</td><td class="gTableRight" id="frM27">$_THREAD_NAME$</td></tr>
<tr id="frM28"><td class="gTableLeft" id="frM29">Thread description:</td><td class="gTableRight" id="frM30">$_THREAD_DESCR$</td></tr>
<?endif?>
<?if($_POLL_QUESTION$)?>
<tr id="frM31"><td class="gTableRight" colspan="2" id="frM32"> </td></tr><tr id="frM33"><td class="gTableLeft" id="frM34">Poll question:</td><td class="gTableRight" id="frM35">$_POLL_QUESTION$</td></tr><tr id="frM36"><td class="gTableLeft" id="frM37">Poll items:<div class="pollHelp">Enter one answer per line. Maximum <b>10</b> answers.</div></td><td class="gTableRight" id="frM38">$_POLL_ANSWERS$</td></tr><tr id="frM40"><td class="gTableLeft" id="frM41">Poll options:</td><td class="gTableRight" id="frM42">$_POLL_ONLY_OPT$ <label for="pollonly">Poll only (no answers allowed in thread)</label><br />$_POLL_MULTI_OPT$ <label for="pollmulty">Enable possibility to choose several answers</label><br />$_POLL_PERIOD_OPT$ Poll period (0 - no limit)</td></tr><tr id="frM43"><td class="gTableRight" colspan="2" id="frM44"> </td></tr>
<?endif?>
<tr id="frM56"><td width="25%" class="gTableLeft" id="frM57" valign="top">Message text:<div class="smilesPart">$SMILES$</div></td><td class="gTableRight" id="frM58">$BBCODES$ $_MESSAGE$</td></tr>
<?if($MESSAGE_OPTIONS_FLAG$)?>
<tr id="frM14"><td class="gTableLeft" id="frM15">Message options:</td><td class="gTableRight" id="frM16">
<?if($_HTML_OPT$)?>
$_HTML_OPT$ <label for="ahtml">Enable HTML tags</label><br />$_MAKE_BR_OPT$ <label for="frmt">Substitute line feeds by the tag <b><BR></b></label><br>
<?endif?>
<?if($_EDITED_OPT$)?>
$_EDITED_OPT$ <label for="edited">Add inscription "Edited..." to this message?</label><br />
<?endif?>
<?if($_SMILES_OPT$)?>
$_SMILES_OPT$ <label for="smon">Enable smileys</label><br />
<?endif?>
<?if($_SIGNATURE_OPT$)?>
$_SIGNATURE_OPT$ <label for="sgon">Enable signature</label><br />
<?endif?>
<?if($_SUBSCRIBE_OPT$)?>
$_SUBSCRIBE_OPT$ <label for="sbon">Enable e-mail notifications about answers</label><br />
<?endif?>
</td></tr>
<?endif?>
<?if($MODER_OPTIONS_FLAG$)?>
<tr id="frM6"><td class="gTableLeft" id="frM7">Thread options:</td><td class="gTableRight" id="frM8">
<?if($_FIRSTONTOP_OPT$)?>
$_FIRSTONTOP_OPT$ <label for="firstontop">Make the first message a heading (display on all pages)</label><br />
<?endif?>
<?if($_ONTOP_OPT$)?>
$_ONTOP_OPT$ <label for="isontop">Thread always on top</label><br />
<?endif?>
<?if($_CLOSED_OPT$)?>
$_CLOSED_OPT$ <label for="isclosed">Closed thread</label>
<?endif?>
</td></tr>
<?endif?>
<?if($_FILES_UPLOADER$)?>
<tr id="frM50"><td class="gTableLeft" id="frM51">Attach file: <span style="font-size:7pt;">(not more than <b>$FILE_MAX_SIZE$</b>Kb)</span></td><td class="gTableRight" id="frM52">$_FILES_UPLOADER$</td></tr>
<?endif?>
<?if($_SECURITY_CODE$)?>
<tr id="frM45"><td class="gTableLeft" id="frM46">Security code:</td><td class="gTableRight" id="frM47">$_SECURITY_CODE$</td></tr>
<?endif?>
<tr id="frM59"><td class="gTableRight" colspan="2" align="center" id="frM60"><input style="width:110px;" id="frF15" class="postPreview" type="button" value="View" onclick="prepost();" /> <input type="submit" id="frF16" name="sbm" style="width:150px;font-weight:bold;" class="postSubmit" value="$SUBMIT_SIGN$" /> <input style="width:110px;" id="frF17" class="postReset" type="reset" value="Cancel" /></td></tr>
</table>
</div></div><div class="gDivBottomLeft"></div><div class="gDivBottomCenter"></div><div class="gDivBottomRight"></div>

Hey friends please help if some one know how to do this please explain.

Pay more attention to the posts...
Read the post Angel7 made.

1. To CSS
Code
.thDescr,
.threadDescr {display:none}
#frM30 img {opacity:.33; -moz-opacity: 0.33; filter: alpha(opacity=33);}
#frM30 img:hover {opacity:.5; -moz-opacity: 0.5; filter: alpha(opacity=50);}
#frM30 img.selectedImg {opacity:1; ; -moz-opacity: 1; filter: alpha(opacity=100);}

You can change them as you want.

2. Forum template, after $BODY$
Code
<script type="text/javascript">$('.thDescr').each(function(){
var s = $(this).html().match( /sml\[(\w+)\]/ );
$(this).show();
if (s==null) return;
var name = s[1];
s = s[0];
$(this).html( $(this).html().replace(s,'') );
if( $(this).html()=='()' ) $(this).html('');
if( $('table.gTable:first td.gTableTop div.gTopCornerRight + img').size()==0 ) $('table.gTable:first td.gTableTop div.gTopCornerRight').after('<img src="/images/threadIcons/'+name+'.png" /> ');
})
$('.threadDescr').each(function(){
var s = $(this).html().match( /sml\[(\w+)\]/ );
$(this).show();
if (s==null) return;
var name = s[1];
s = s[0];
$(this).html( $(this).html().replace(s,'') );
$(this).parent().prev().find('img').attr('src','/images/threadIcons/'+name+'.png');
});
</script>

Then you need to upload your icons to the folder "images/threadIcons". Names consist of only letters, numbers and _ .

3. Open template of adding message form. Replace $_THREAD_DESCR$ with
Code
<input type="text" id="threadAbout" value="" class="postDescrFl" size="60" maxlength="50" />
<img src="http://s3.ucoz.net/img/fr/ic1/thread.gif" alt="" class="selectedImg" />
<img src="/images/threadIcons/image1.png" alt="Image1" />
...
<img src="/images/threadIcons/imageN.png" alt="ImageN" />
<div style="display:none">$_THREAD_DESCR$</div>

where http://s3.ucoz.net/img/fr/ic1/thread.gif is a default picture.

And then add to the end of template:
Code
<?if($_THREAD_NAME$)?>
<script type="text/javascript">
$('#frF3').css('width','auto').attr('size', 60);
$('#frM30 img').click(function(){
$('#frM30 .selectedImg').removeClass('selectedImg');
$(this).addClass('selectedImg')
});
if( $('#frF4').val()!='' ){
if( $('#frF4').val().match( /sml\[\w+\]/ ) ){
$('#threadAbout').val( $('#frF4').val().replace( $('#frF4').val().match( /sml\[(\w+)\]/ )[0], '' ) );
$('#frM30 .selectedImg').removeClass('selectedImg');
$('#frM30 img[src$="'+ $('#frF4').val().match( /sml\[(\w+)\]/ )[1] +'.png"]').addClass('selectedImg');
} else $('#threadAbout').val( $('#frF4').val() );
}
function checksubmit(){
var s = $('#frM30 .selectedImg').attr('src').match( /\/(\w*)\.png/i );
if( s!=null ) s = 'sml['+s[1]+']'; else s='';
$('#frF4').val( s + $('#threadAbout').val() );
return true;
}</script>
<?endif?>

Source: helper.RU (translation: Angel7)
uCoz rocks <3

awesome script, but i am getting one error,
After selecting the icon on the create form of message it is not displayed in the forum list. Can you help plz...