Just copy and past it in a test page first its working
Step 1: add it in your aspx page
<div class="divRegistration">
<div class="divleft">
<label>
full name :<span class="spanstar">*</span></label>
</div>
<div class="divright">
<asp:textbox id="txtfullname" runat="server" maxlength="30"></asp:textbox>
<span id="nameError" class="spanerror"></span>
</div>
</div>
<div class="divRegistration">
<div class="divleft">
<label>
Contact No :<span class="spanstar">*</span></label>
</div>
<div class="divright">
<asp:textbox id="txtContactNo" runat="server" maxlength="30"></asp:textbox>
<span id="Span1" class="spanerror"></span>
</div>
</div>
<asp:button id="btn" runat="server" text="submit" onclientclick="return AllValidation();" OnClick="btn_Click" />
Step 2: in head tag
<script>
function AllValidation()
{
if(emptelephoneno())
{
if(emptelephoneno1())
{
return true;
}
}
return false;
}
function emptelephoneno()
{
var elem = document.getElementById('<%=txtfullname.ClientID%>');
if (elem.value.length == 0)
{
elem.style.border = '1px solid red';
document.getElementById('nameError').innerHTML = "Please Enter Your First Name";
return false;
}
else
{
elem.style.border = '';
document.getElementById('nameError').innerHTML = "";
}
return true;
}
function emptelephoneno1()
{
var elem1 = document.getElementById('<%=txtContactNo.ClientID%>');
if (elem1.value.length == 0)
{
elem1.style.border = '1px solid red';
document.getElementById('Span1').innerHTML = "Please Enter Your First Name";
return false;
}
else
{
elem1.style.border = '';
document.getElementById('Span1').innerHTML = "";
}
return true;
}
</script>