Hi,I want to retain value of checkbox,when some validation error occours.
In this i am calling a function checkCheckBoxes() & want to call this function
when validation error occours.

<input type="checkbox" name="chk1"  onclick='checkCheckBoxes() <?php if (isset($_POST['chk1'])) echo ' checked="checked"'; ?>'/>check for Birth year only

function

function checkCheckBoxes() 
{
	
	if(document.myform.chk1.checked)
    {
     document.myform.day.disabled=true;
     document.myform.Month.disabled=true;
    }
    else
    {
       document.myform.day.disabled=false;
       document.myform.Month.disabled=false;
    }
}

try this

<input type="checkbox" name="chk1"  onclick='checkCheckBoxes()' value="1" <?php if ($_POST['chk1']=="1") echo 'checked="checked"'; ?>/>check for Birth year only

still function is not working.
only checkbox is selected after validation failure.

function is running fine here

I think you have problem with

<input type="checkbox" name="chk1"  onclick='checkCheckBoxes()' />check for Birth year only

or if you have chrome, then open tool> java script console, there you will able to see error.

function is running fine here

I think you have problem with

<input type="checkbox" name="chk1"  onclick='checkCheckBoxes()' />check for Birth year only

or if you have chrome, then open tool> java script console, there you will able to see error.

Thanks,function is working fine.but my problem is:
I have 3 drop down list.when a user check checkbox,it call checkCheckBoxes() function & disable first 2 dropdown.
What i am trying,
suppose a user check the checkbox & there is some validation error while submiting,
then the checkbox remain check & disable drop down remain disable
my problem is disable drop down does not remain disable.

post complete code, and let me know when logic fails (what you input and what not)

Check the error console in your browser for javascript errors and post the error here...

suppose a user check the checkbox & there is some validation error while submiting,
Are you validating form in PHP side?

post complete code, and let me know when logic fails (what you input and what not)

<tr>
<td align="right">जन्म तिथि:&nbsp;&nbsp;</td>
<td>
<div style="float:left; width:auto;">
<select name="year" id="year">
    <?php
		for($y=1920; $y<=2012; $y++)
		{
	?>
		<option value="<?php echo $y; ?>" <?php if($y==$_POST["year"]) echo "selected"; ?> > <?php echo $y; ?> </option>
    <?php
		}
    ?>
    </select>

</div><?php
if(isset($_POST['submit']))
			$ccountry = $_POST['Month'];
			else
			$ccountry = '';
							
		 
		 $country_to_preselect = $ccountry;
		
						
			$options_month = array
			(
			''	 => '-- Select --', 
		         "1" => 'January',
			 "2" => 'Feb',
			 "3" => 'March',
			 "4"=>'April',
		         "5"=>'May',
		         "6"=>'June',
		         "7"=>'july',
		         "8"=>'August',
		         "9"=>'September',
		         "10"=>'October',
		         "11"=>'November',
		         "12"=>'December'
						);
            	?>

<div style="float:left; width:auto; padding-left:10px;">
	<select name="Month" onchange="showdate(document.getElementById('year').value, this.value);">
	<?php
		foreach ($options_month as $index => $value)
			{
			   echo '    <option value="' . $index . '"';
				 if ($index == $country_to_preselect)
				   {
						  echo ' selected ';
				   }
				    echo '>' . $value . '</option>';
						}
					?>
	</select>
</div>
<div id="txtHint" style="width: 43px; float:left; padding-left:10px;">
 <select name="day" id="day">
    <?php
		for($d=1; $d<=31; $d++)
		{
	?>
		<option value="<?php echo $d; ?>" <?php if($d==$_POST["day"]) echo "selected"; ?> > <?php echo $d; ?> </option>
    <?php
		}
    ?>
    </select>
</div>
&nbsp;<input type="checkbox" name="chk1"  onclick='checkCheckBoxes()' value="1" <?php if ($_POST['chk1']=="1") echo 'checked="checked"'; ?>/>check for Birth year only</td>
</tr>

Js code

function checkCheckBoxes() 
{
	
	if(document.myform.chk1.checked)
    {
     document.myform.day.disabled=true;
     document.myform.Month.disabled=true;
    }
    else
    {
       document.myform.day.disabled=false;
       document.myform.Month.disabled=false;
    }
}

function showdate(yr, mon)
{

xmlhttp=GetXmlHttpObject();
if (xmlhttp==null)
{
alert ("Browser does not support HTTP Request");
return;
}
var url="select-date.php";
url=url+"?yr="+yr;
url=url+"&mon="+mon;
xmlhttp.onreadystatechange=stateChanged;
xmlhttp.open("GET",url,true);
xmlhttp.send(null);
}

at the end of page load write following js code

<script lang='javascript'>
checkCheckBoxes();
</script>