<script language="Javascript">
function sem(form){
var okem=form.st.value.match(/\b(^(\S+@).+((\.com)|(\.net)|(\.edu)|(\.mil)|(\.gov)|(\.org)|(\..{2,2}))$)\b/gi);
if (okem){
window.location = "mailto:"+form.st.value+"?subject="+form.sb.value+"&body="+form.ta.value;
}
else{
alert("Upišite ispravnu email adresu.");
form.st.focus();
form.st.select();
}
}
</script>

<form action="mailto:franjo@example.org">
  <table border="0">
    <tr>
      <td><font color="#FF6600">Prima email:</font></td>
      <td><input type="text" name="st" value size="30"></td>
    </tr>
    <tr>
      <td><font color="#FF6600">Subject:</font></td>
      <td><input type="text" name="sb" value="Vidi ovo" size="30"></td>
    </tr>
    <tr>
      <td valign="top"><font color="#FF6600">Text:</font></td>
      <td><textarea name="ta" Rows="4" Cols="25">Posjeti ovaj site: http://forum.burek.com/</textarea></td>
    </tr>
  </table>
  <p><input type="Button" value="Pošalji Email" onClick="javascript:sem(this.form);"></p>
</form>