se om billed er et rødt kryds

Du kan bruge onerror eventen på img tagget

<img src="dethergiverheltsikkertfejl" onerror="alert(this.id)" id="23">

Summary: Hide the dreaded "Red X" box caused by broken images in posts.

Details:
This script uses the Internet Explorer-only filesize property of images to determine whether they have been properly loaded.

HEAD (box #1):

<script type="text/javascript">
/* HIDE BROKEN IMAGES */
function hideBroken() {
var showAlt = true;
ai = document.getElementsByTagName("img");
for (im=0; im < ai.length; im++) {
try {
if (ai[im].fileSize <= 0 && ai[im].src.match(".jpg$|.gif$|.png$|.bmp$")) {
if ( ai[im].alt != "" && showAlt ) {
ax = document.createTextNode("(" + ai[im].alt + ")");
ai[im].parentNode.insertBefore(ax, ai[im]);
}
ai[im].style.display = "none";
}
} catch (e) {}
}
}
/* END HIDE BROKEN IMAGES */
</script>

Change the variable "showAlt" to false to not replace the image with it's alt text (where available).

FOOTER (box #4):

<script type="text/javascript">
/* HIDE BROKEN IMAGES */
setTimeout(hideBroken, 1000);
/* END HIDE BROKEN IMAGES */
</script>

Change 1000 to the number of seconds you want it to wait before looking for non-loading images, times 1000. So for 3 seconds, you'd change it to 3000.