求教论坛发帖预览时提示“document.forms.0.subject.value"为空或不是对象的出错原因？

[yfy3900]

function Cra() {
var FoundErrors = '';
var enterURL = prompt(text_enter_ra, "http://");
if (!enterURL) {
FoundErrors += "\n" + error_no_url;
}
if (FoundErrors) {
alert("错误！"+FoundErrors);
return;
}
var ToAdd = "[RA]"+enterURL+"[/RA]";
document.frmAnnounce.Content.value+=ToAdd;
document.frmAnnounce.Content.focus();
}



function Cfanzi() {
fontbegin="[xray]";
fontend="[/xray]";
fontchuli();
}

function Cwma() {
var FoundErrors = '';
var enterURL = prompt(text_enter_wma, "http://");
if (!enterURL) {
FoundErrors += "\n" + error_no_url;
}
if (FoundErrors) {
alert("错误！"+FoundErrors);
return;
}
var ToAdd = "[wma]"+enterURL+"[/wma]";
document.frmAnnounce.Content.value+=ToAdd;
document.frmAnnounce.Content.focus();
}


function Cmarquee() {
fontbegin="[move]";
fontend="[/move]";
fontchuli();
}
function Cfly() {
fontbegin="[fly]";
fontend="[/fly]";
fontchuli();
}

function paste(text) {
if (opener.document.frmAnnounce.Content.createTextRange && opener.document.frmAnnounce.Content.caretPos) {
var caretPos = opener.document.frmAnnounce.Content.caretPos;
caretPos.text = caretPos.text.charAt(caretPos.text.length - 1) == ' ' ?
text + ' ' : text;
}
else opener.document.frmAnnounce.Content.value += text;
opener.document.frmAnnounce.Content.focus(caretPos);
}

function showsize(size){
fontbegin="[size="+size+"]";
fontend="[/size]";
fontchuli();
}

function showfont(font){
fontbegin="[face="+font+"]";
fontend="[/face]";
fontchuli();
}

function showcolor(color){
fontbegin="[color="+color+"]";
fontend="[/color]";
fontchuli();
}

function fontchuli(){
if ((document.selection)&&(document.selection.type == "Text")) {
var range = document.selection.createRange();
var ch_text=range.text;
range.text = fontbegin + ch_text + fontend;
}
else {
document.frmAnnounce.Content.value=fontbegin+document.frmAnnounce.Content.value+fontend;
document.frmAnnounce.Content.focus();
}
}

function Cguang() {
var FoundErrors = '';
var enterSET = prompt(text_enter_guang1, "255,red,2");
var enterTxT = prompt(text_enter_guang2, "文字");
if (!enterSET) {
FoundErrors += "\n" + error_no_gset;
}
if (!enterTxT) {
FoundErrors += "\n" + error_no_gtxt;
}
if (FoundErrors) {
alert("错误！"+FoundErrors);
return;
}
var ToAdd = "[glow="+enterSET+"]"+enterTxT+"[/glow]";
document.frmAnnounce.Content.value+=ToAdd;
document.frmAnnounce.Content.focus();
}

function Cying() {
var FoundErrors = '';
var enterSET = prompt(text_enter_guang1, "255,blue,1");
var enterTxT = prompt(text_enter_guang2, "文字");
if (!enterSET) {
FoundErrors += "\n" + error_no_gset;
}
if (!enterTxT) {
FoundErrors += "\n" + error_no_gtxt;
}
if (FoundErrors) {
alert("错误！"+FoundErrors);
return;
}
var ToAdd = "[SHADOW="+enterSET+"]"+enterTxT+"[/SHADOW]";
document.frmAnnounce.Content.value+=ToAdd;
document.frmAnnounce.Content.focus();
}

ie = (document.all)? true:false
if (ie){
function ctlent(eventobject){if(event.ctrlKey && window.event.keyCode==13){this.document.frmAnnounce.submit();}}
}
function DoTitle(addTitle) {
var revisedTitle;
var currentTitle = document.frmAnnounce.subject.value;
revisedTitle = currentTitle+addTitle;
document.frmAnnounce.subject.value=revisedTitle;
document.frmAnnounce.subject.focus();
return; }

function insertsmilie(smilieface){

document.frmAnnounce.Content.value+=smilieface;
}
function gopreview()
{
document.forms[1].title.value=document.forms[0].subject.value;
document.forms[1].body.value=document.forms[0].Content.value;
var popupWin = window.open('preview.asp', 'preview_page', 'scrollbars=yes,width=750,height=450');
document.forms[1].submit()
}

[panyee]

document.forms[0].subject.value

[yfy3900]

怎么了？

[yfy3900]

谢谢参与