IIRC, the unique ID of an entry == 256 * itemid + anum. But this is not guaranteed to remain (or even still be!) the case, so if you have obtained the ID of an entry by other means, use that when you wish to do something with it (say, getevents).

(FWIW, 256*1 + 203 indeed == 459.)

And so does the number in the hyperlink is guaranteed to be that unique number?

The URL is guaranteed to bring a browser to the entry, but I don't think the protocol is guaranteed to keep honoring that number you extract from the URL (or indeed, continue to supply a URL of that particular form forever).

Zilla is down so I can't make sure, but there's a bug about this issue there.

Ok, thanks =)

As gaal said, (256 * anum + itemid) = the ID number of the post used on the site, in URLs and such. The anum is used so that somebody can't figure out how many hidden posts you are posting just by looking at the URLs.

The itemid is not useless, it is very useful, because if you are writing a client you can save it and use it in future requests to modify the entry you just posted. I hate that sentence in the documentation.

And if I own an account how could I calculate itemid having link to some post?

For the record, I had the equation wrong, it is (256 * itemid + anum) = webid.

If you know bit shifting, then (256 * itemid) is the same as (itemid << 8).

If you have the webid, you can just shift it eight bits to the right to get the itemid. In other words, itemid = (webid >> 8). You don't need the anum at all to convert in this direction.

OK, I understand, thank you =)