필드가 정확히 뭐인지 모르겠지만..정확하지않으오나
<script language="javascript">
function onChangeKey() {

var pattern = new RegExp('[^가-힣a-zA-Z0-9]', 'i');
if (fwrite.stx.value) {
if (pattern.exec(fwrite.stx.value) != null) {
alert("'"+fwrite.stx.value + "'는 사용할수 없습니다. \n\n 올바르게 입력하세요 \n\n 특수문자,공백,한문,불가.");
return;
}
 else {
fwrite.stx.focus();
}
}

var wr_name = document.fwrite.wr_name.value;
var stx = document.fwrite.stx.value;





if (wr_1 == "" && wr_2 == "" && stx == "") {
alert("검색조건을 선택하세요!!");
return false;
}





else {
if (wr_name == "" && stx2 != "")  {
document.fwrite.stx.value = stx;
}
else {
document.fwrite.stx.value = wr_name + " " + stx;
}
document.fwrite.submit();
}
}


//--> 
</script>
<form name=fwrite method=get style="margin:0px;">
<input type=hidden name=bo_table value="<?=$bo_table?>">
<input type=hidden name=sca value="<?=$sca?>">
<input type=hidden name=sfl value="wr_name">
<input type=hidden name=sca value="and">
<input type=text class="input_text" name=stx maxlength=15 size=10 style="width:130px;" class=input itemname="제목"  value="">
<input type=text class="input_text" name=wr_name maxlength=15 size=10 style="width:130px;" class=input itemname="글쓴이"  value="">
<input type=image onClick="onChangeKey();return false;" src="<?=$board_skin_path?>/img/btn_search.gif" align=absmiddle border=0>
</form>
이렇게 해보시면될겁니다.