I was hoping that the image's "location" property would be set
appropriately based on the redirect from big.oscar, but unfortunately
that's not the case. So the only thing I could think of was to have a
tiny offline image, and use the image's "height" property to tell in
the onload handler whether it was the online or offline image that
loaded. Fortunately, this worked pretty well. Here's a simple example
page that demonstrates this behavior:
if (document.getElementById("i").height <= 2)
document.getElementById("s").style.fontStyle = "italic";
<img id="i" onload="imgload()" border="0"
and the output:
This italicizes the text if the user "nosuchuser" is offline. This is
just a simple example, from here you can do lots of things, such as
add/change a hyperlink, etc.