if (document.selection) {
 this.focus();
 document.selection.createRange().text = smiley;
 }
 else if (this.selectionStart || this.selectionStart == '0') {
 var cursorPos = this.selectionEnd + smiley.length;
 this.value = this.value.substring(0, this.selectionStart) + smiley + this.value.substring(this.selectionEnd);
 this.selectionStart = this.selectionEnd = cursorPos;
 }
 else {
 this.value = this.value + smiley;

if(typeof tinyMCE != "undefined" ) tinyMCE.execCommand('mceInsertContent',false, smiley);
 else{
 // старый код сюда
.....
}