Mobile number validation

To valid a phone number like
XXX-XXX-XXXX
XXX.XXX.XXXX
XXX XXX XXXX

function phonenumber(inputtxt)
{
var phoneno = /^(?([0-9]{3}))?[-. ]?([0-9]{3})[-. ]?([0-9]{4})$/;
if((inputtxt.value.match(phoneno))
{
return true;
}
else
{
alert("message");
return false;
}
}

If you want to use a + sign before the number in the following way
+XX-XXXX-XXXX
+XX.XXXX.XXXX
+XX XXXX XXXX
use the following code.

function phonenumber(inputtxt)
{
var phoneno = /^+?([0-9]{2}))?[-. ]?([0-9]{4})[-. ]?([0-9]{4})$/;
if((inputtxt.value.match(phoneno))
{
return true;
}
else
{
alert("message");
return false;
}
}

CSS Code

li {list-style-type: none;
font-size: 16pt;
}
.mail {
margin: auto;
padding-top: 10px;
padding-bottom: 10px;
width: 400px;
background : #D8F1F8;
border: 1px soild silver;
}
.mail h2 {
margin-left: 38px;
}
input {
font-size: 20pt;
}
input:focus, textarea:focus{
background-color: lightyellow;
}
input submit {
font-size: 12pt;
}
.rq {
color: #FF0000;
font-size: 10pt;
}