eBay will most assuredly change the listing description iframe content.
So the example below is a point-in-time snapshot. You should also example a listing yourself to see what the latest is.
Regardless of content, you shouldn't be affected by what eBay provides as long as your top level html tag is a <div>.
The code below looks like a lot, but you needed concern yourself with the gory details.
Just scroll down to line 168 and you'll see where your template will be inserted.
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

<html>
<head>
    <meta name="generator" content=
    "HTML Tidy for Linux/x86 (vers 11 February 2007), see www.w3.org">
    <meta http-equiv="Last-Modified" content="Wed, 14 Dec 2011 11:16:59 GMT">
    <meta http-equiv="Expires" content="Fri, 14 Dec 2012 11:16:59 GMT">

    <title></title>
</head>

<body>
    <script type="text/javascript">
var ebayItemID=110094717828;var ct=true;var sellerId='ultracartjohn';var domain='sandbox.ebay.com';var ebayItemRevisionTime=1323369224000;var ebayAskSellerURL='http://contact.sandbox.ebay.com/ws/eBayISAPI.dll?ShowSellerFAQ&frm=284&rt=nc&iid=110094717828&ssPageName=PageSellerM2MFAQ_VI&redirect=0&requested=ultracartjohn';var bStoresNav=false;var isPM=false;
    </script><script language='javascript' type="text/javascript">

    var sUrl = "http://cgi.sandbox.ebay.com/ws/eBayISAPI.dll?ViewItemDescV4&s2=0&nv=2&vct=1"; 
    </script><script type="text/javascript">

    /**ThinViewJs**/
    var ifr = function () {};
    ifr.browserDetect = function () {
    this.bFirefox = this.bWebTV = this.bOpera = this.bNav = this.bIE = this.bSafari = this.bWin = this.bMac = this.bMacppc = this.bMactel = this.bWinXp = this.bXpSp2 = this.bAOL = this.bVista = false;
    this.iVer = this.fVer = -1;
    this.fMinorVer = 0;
    this.init = function () {
        var nv = navigator,
            agt = nv.userAgent.toLowerCase(),
            i = 0,
            ver;
        with(this) {
            if (agt.indexOf('webtv') != -1) {
                bWebTV = true;
                i = agt.indexOf('webtv/') + 6;
            } else if (agt.indexOf('firefox') != -1) {
                bFirefox = true;
                i = agt.lastIndexOf('firefox') + 8;
            } else if (agt.indexOf('safari') != -1) {
                bSafari = true;
                i = agt.lastIndexOf('safari') + 7;
            } else if (typeof (window.opera) != 'undefined') {
                bOpera = true;
                i = agt.lastIndexOf('opera') + 6;
            } else if (nv.appName == 'Netscape') {
                bNav = true;
                i = agt.lastIndexOf('/') + 1;
            } else if (agt.indexOf('msie') != -1) {
                bIE = true;
                i = agt.indexOf('msie') + 4;
                if ((agt.indexOf('aol') != -1) || (agt.indexOf('america online') != -1)) bAOL = true;
            }
            ver = bOpera ? window.opera.version() : agt.substring(i);
            iVer = parseInt(ver);
            fVer = parseFloat(ver);
            fMinorVer = fVer - iVer;
            bWin = (agt.indexOf('win') != -1);
            bWinXp = (bWin && (agt.indexOf('windows nt 5.1') != -1));
            bVista = (bWin && (agt.indexOf('windows nt 6.0') != -1));
            bXpSp2 = (bWinXp && (agt.indexOf('sv1') != -1));
            bMac = (agt.indexOf('mac') != -1);
            bMacppc = (bMac && ((agt.indexOf('ppc') != -1) || (agt.indexOf('powerpc') != -1)));
            bMactel = (bMac && (agt.indexOf('intel') != -1));
        }
    }
    this.init();
    return this;
    }
    var ifr = function () {};
    ifr.ebayAegis = function () {
    window.setTimeout = function (pFunc, pStart) {
        //nothing 
    }
    window.setInterval = function (pFunc, pInt) {
        //nothing 
    }
    };
    window.onerror = function () {
    //nothing 
    };
    ifr.setHash = function () {
    var oCl = ifr.browserDetect();
    var re = new RegExp('^http\://cgi\.');
    var re2 = new RegExp('^(http\://www\.)([a-z]{2}\.)?([0-9a-z]{5}\.)?([a-z]{2}\.)?([a-z]{4}\.)([a-z]{3}|[a-z]{2})(\.[a-z]{2})?(/itm/)');
    var re3 = new RegExp('^http\://vi\.');
    var rf = window.document.referrer;
    if (oCl.bSafari) {
        if ((rf.toString().match(re) !== null) || (rf.toString().match(re2) !== null)) {
            parent.location.replace(rf + '#bl');
        }
    } else {
        if (rf.toString().match(re3) !== null) {
            parent.frames[0].location.replace(sUrl + '&c=1#bl');
        }
    }
    };
    ifr.process = function (piTime) {
    var oCl = ifr.browserDetect();
    var browser, os;
    if (oCl.bWebTV) {
        browser = 'webtv';
    } else if (oCl.bFirefox) {
        browser = 'firefox';
    } else if (oCl.bSafari) {
        browser = 'safari';
    } else if (oCl.bOpera) {
        browser = 'opera';
    } else if (oCl.bNav) {
        browser = 'netscape';
    } else if (oCl.bIE) {
        browser = 'msie';
    }
    if (oCl.bWin) {
        os = 'windows';
    } else if (oCl.bWinXp) {
        os = 'windows xp';
    } else if (oCl.bVista) {
        os = 'windows vista';
    } else if (oCl.bXpSp2) {
        os = 'windows xp sp 2';
    } else if (oCl.bMac) {
        os = 'mac';
    } else if (oCl.bMacppc) {
        os = 'mac powerpc';
    } else if (oCl.bMactel) {
        os = 'mac intel';
    }
    };
    ifr.initClientLog = function () {
    var img = new Image();
    var bl = new Date().getSeconds();
    window.onerror = function (message, url, line) {
        if (typeof (window.iErrorCt) == 'undefined' && (typeof (errorLogUrl) !== 'undefined')) {
            img.src = errorLogUrl + '&item=' + ebayItemID + '&difJserror=1' + '&difJserrorDesc=' + message + ' on line ' + line + '&bs=' + browser + ' ' + oCl.fVer + '&os=' + os + '&seller=' + sellerId;
            window.iErrorCt = 1;
            return true;
        }
    };
    if (typeof (piTime) !== 'undefined') {
        if ((typeof (piTime) !== null) && (typeof (window.iErrorCt) == 'undefined')) {
            var lt = (bl - piTime) / 1000;
            if (lt > clientErrorThresholdTime) {
                img.src = errorLogUrl + '&item=' + ebayItemID + '&difUrlResp=' + lt + '&bs=' + browser + ' ' + oCl.fVer + '&os=' + os + '&seller=' + sellerId;
            }
        }
    }
    if (typeof (clientErrorLog) !== 'undefined') {
        if (clientErrorLog) {
            ifr.setHash();
            ifr.process(null);
            window.onunload = function () {
                window.onerror = null;
            };
        }
    }
    };
    </script>

    <table align="center" style="border-spacing: 0px;width:100%;">
        <tr>
            <td>
                <div id="EBdescription">
                    <!-- Begin Description -->



                    YOUR EBAY LISTING TEMPLATE WILL GO HERE!! 



                    <!-- End Description -->
                </div>
            </td>
        </tr>
    </table><span id="closeHtml"></span> <script type="text/javascript">

    /**ThinViewJs**/
    var ifr = function () {};
    ifr.browserDetect = function () {
    this.bFirefox = this.bWebTV = this.bOpera = this.bNav = this.bIE = this.bSafari = this.bWin = this.bMac = this.bMacppc = this.bMactel = this.bWinXp = this.bXpSp2 = this.bAOL = this.bVista = false;
    this.iVer = this.fVer = -1;
    this.fMinorVer = 0;
    this.init = function () {
        var nv = navigator,
            agt = nv.userAgent.toLowerCase(),
            i = 0,
            ver;
        with(this) {
            if (agt.indexOf('webtv') != -1) {
                bWebTV = true;
                i = agt.indexOf('webtv/') + 6;
            } else if (agt.indexOf('firefox') != -1) {
                bFirefox = true;
                i = agt.lastIndexOf('firefox') + 8;
            } else if (agt.indexOf('safari') != -1) {
                bSafari = true;
                i = agt.lastIndexOf('safari') + 7;
            } else if (typeof (window.opera) != 'undefined') {
                bOpera = true;
                i = agt.lastIndexOf('opera') + 6;
            } else if (nv.appName == 'Netscape') {
                bNav = true;
                i = agt.lastIndexOf('/') + 1;
            } else if (agt.indexOf('msie') != -1) {
                bIE = true;
                i = agt.indexOf('msie') + 4;
                if ((agt.indexOf('aol') != -1) || (agt.indexOf('america online') != -1)) bAOL = true;
            }
            ver = bOpera ? window.opera.version() : agt.substring(i);
            iVer = parseInt(ver);
            fVer = parseFloat(ver);
            fMinorVer = fVer - iVer;
            bWin = (agt.indexOf('win') != -1);
            bWinXp = (bWin && (agt.indexOf('windows nt 5.1') != -1));
            bVista = (bWin && (agt.indexOf('windows nt 6.0') != -1));
            bXpSp2 = (bWinXp && (agt.indexOf('sv1') != -1));
            bMac = (agt.indexOf('mac') != -1);
            bMacppc = (bMac && ((agt.indexOf('ppc') != -1) || (agt.indexOf('powerpc') != -1)));
            bMactel = (bMac && (agt.indexOf('intel') != -1));
        }
    }
    this.init();
    return this;
    }
    var oCl = ifr.browserDetect();
    if (oCl.bFirefox) {
    ifr.init(1);
    }
    ifr.addLoadEvent = function (func) {
    var oldonload = window.onload;
    if (typeof window.onload != 'function') {
        window.onload = func;
    } else {
        window.onload = function () {
            if (oldonload) {
                oldonload();
            }
            func();
        }
    }
    };
    ifr.addLoadEvent(function () {
    ifr.init(2);
    });
    ifr.init = function (callerId) {
    var lastInitCall = '';
    var bSafari = oCl.bSafari;
    var bFirefox = oCl.bFirefox;
    var iVer = oCl.iVer;
    var bWin = oCl.bWin;
    var cTime = new Date().getTime();
    if (!window.bError) {
        var el = new Date().getSeconds();
        var lt = (el - window.bl);
    }
    if (typeof (clientErrorLog) !== 'undefined') {
        if (lt > clientErrorThresholdTime) {
            ifr.process(lt);
        }
    }
    if (((callerId !== 2) && (lastInitCall !== '') && ((cTime - lastInitCall) < 2000)) || (bSafari && (callerId == 1))) {
        return;
    }
    lastInitCall = cTime;
    document.onclick = function (e) {
        e = (e) ? e : ((window.event) ? event : null);
        var elem = (e.target) ? e.target : ((e.srcElement) ? e.srcElement : null);
        var bAnch = true;
        if (typeof (elem.href) == 'undefined') {
            while (elem) {
                elem = elem.parentNode;
                if (elem == null) {
                    bAnch = false;
                    break;
                } else if (elem.tagName == 'A') {
                    break;
                } else if (elem.tagName == 'FORM') {
                    elem.target = '_blank';
                    bAnch = false;
                    break;
                }
            }
        }
        if (bAnch) {
            var str = elem.href.toString(),
                tgt = elem.target.toLowerCase();
            str = str.toLowerCase();
            if (tgt != '_blank' && tgt != '_top' && str.substring(0, 10) != 'javascript' && (!str.match(/.ebaydesc./) && str.substring(0, 1) != '#')) {
                elem.target = '_blank';
            }
            if ((ct) && (str.substring(0, 10) != 'javascript' && (!str.match(/.ebaydesc./) && str.substring(0, 1) != '#'))) {
                var sUrl = 'http://rover.' + domain + '/roverclk/0/0/9?trknvp=sid%3Dp4340.l2879';
                if (ebayItemID !== 'undefined') {
                    sUrl = sUrl + '%26itemid%3D' + ebayItemID;
                }
                if (sellerId !== 'undefined') {
                    sUrl = sUrl + '%26slrid%3D' + sellerId;
                }
                sUrl = sUrl + '%26loc%3D' + str;
                sUrl = sUrl + '%26r%3D' + Math.floor(Math.random() * 6);
                var oImg = new Image();
                oImg.src = sUrl;
            }
        }
    };
    ifr.resizeIt(callerId);
    };
    ifr.setData = function (pSize, callerId) {
    var oCl = ifr.browserDetect();
    var h = pSize[0];
    var w = pSize[1];
    var re = new RegExp('^http\://cgi\.');
    var re2 = new RegExp('^(http\://www\.)([a-z]{2}\.)?([0-9a-z]{5}\.)?([a-z]{2}\.)?([a-z]{4}\.)([a-z]{3}|[a-z]{2})(\.[a-z]{2})?(/itm/)');
    var re3 = new RegExp('^http\://vi\.');
    var rf = window.document.referrer;
    if (oCl.bSafari) {
        if ((rf.toString().match(re) !== null) || (rf.toString().match(re2) !== null)) {
            parent.location.replace(rf + '#ht_' + h + 'wt_' + w);
        }
    } else {
        if (rf.toString().match(re3) !== null) {
            parent.frames[0].location.replace(sUrl + '&c=' + callerId + '#ht_' + h + 'wt_' + w);
        }
    }
    };
    ifr.getSize = function () {
    var oCl = ifr.browserDetect();
    var h, w, rv = [0, 0];
    if (document.all) {
        h = document.body.scrollHeight;
        w = document.body.scrollWidth;
        if (oCl.bIE && oCl.iVer >= 9 && document.getElementById('EBdescription')) {
            h = document.getElementById('EBdescription').scrollHeight;
            var u = document.location.href;
            if (u && u.indexOf('&tid=') != -1 && document.getElementById('ngvi_store_id')) {
                h = document.getElementById('ngvi_store_id').scrollHeight;
            }
            h = h + 40;
        }
    } else {
        h = document.body.offsetHeight;
        if (oCl.bSafari && oCl.iVer >= 523) {
            w = document.body.scrollWidth;
        } else {
            w = document.body.offsetWidth;
            if (window.scrollMaxX !== 0) {
                w += window.scrollMaxX;
            }
        }
    }
    if (isNaN(w)) {
        w = 0;
    }
    if ((oCl.bFirefox && oCl.bWin) && (h > 32000)) {
        h = 32000;
    }
    rv[0] += h;
    rv[1] += w;
    return rv;
    };
    ifr.resizeIt = function (callerId) {
    var oCl = ifr.browserDetect();
    var size = ifr.getSize();
    if (size) {
        if (window['postMessage'] && isPM) {
            parent.postMessage(size, '*');
        } else {
            if (!oCl.bSafari) {
                var rf = window.document.referrer;
                var re = new RegExp('^http\://cgi\.');
                var re2 = new RegExp('^(http\://www\.)([a-z]{2}\.)?([0-9a-z]{5}\.)?([a-z]{2}\.)?([a-z]{4}\.)([a-z]{3}|[a-z]{2})(\.[a-z]{2})?(/itm/)');
                if ((rf.toString().match(re) !== null) || (rf.toString().match(re2) !== null)) {
                    parent.resizeFrame(size);
                }
            }
            ifr.setData(size, callerId);
        }
    };
    }
    </script>
</body>
</html>
Browser not supported
