Oops, just found that you have some kind of an anti-spam code in your php that uses different textarea, so here is a more advanced fix:
Locate the places in source and
add/do these changes in the script
...
<div id="pagebody">
<script language="JavaScript" type="text/javascript">
<!--
var current_message = null;
window.onload = function () {
if ((document.post.zprava1.style)&&(document.post.zprava1.style.display!="none")) {
current_message=document.post.zprava1;
} else if ((document.post.zprava2.style)&&(document.post.zprava2.style.display!="none")) {
current_message=document.post.zprava2;
} else if ((document.post.zprava3.style)&&(document.post.zprava3.style.display!="none")) {
current_message=document.post.zprava3;
} else if ((document.post.zprava4.style)&&(document.post.zprava4.style.display!="none")) {
current_message=document.post.zprava4;
} else if ((document.post.zprava5.style)&&(document.post.zprava5.style.display!="none")) {
current_message=document.post.zprava5;
}
}
// bbCode control by
// subBlue design
...
function checkForm() {
formErrors = false;
if (current_message.value.length < 2) {
//if (document.post.message.value.length < 2) {
formErrors = "You must enter a message when posting.";
}
...
function emoticon(text) {
var txtarea =
current_message; //document.post.message;
...
function bbfontstyle(bbopen, bbclose) {
var txtarea =
current_message; //document.post.message;
...
function bbstyle(bbnumber) {
var txtarea =
current_message; //document.post.message;