<script>
function strpos( haystack, needle, offset){
    var i = (haystack+'').indexOf( needle, offset ); 
    return i===-1 ? false : i;
}
function prov_num() {
    var number = document.getElementById("input1"); 
    var chek = strpos(number.value, '+', 0);
    var chek1 = strpos(number.value, '0', 0);

    if (chek === 0 || chek1 === 0)
    {
      alert ('Wrong number!!!');
    } 
    else 
    {
      alert ('Good number!!!'); // или переадресация на нужную страницу, например
    }
}
</script>

 <FORM NAME="form1"> 
 <input type="text" name="phonne" id="input1" size="10" style="width: 150px">
 <input type="submit" name="submit" value="Start" onclick="prov_num()"> 
 </FORM>