I would only suggest this if you run your own webserver as then you can skip the uploading part and just script an on *:TEXT: to write to a .txt file like so
<mIRC>$timestamp $+(<,$nick,>) $1-</mirc>
Then on your website you can either just make the user refresh manually and load the maximum lines you want to see in a div using document.
getElementsByTagName('mIRC') to reference to all the lines. Reason to do it this way is that you can parse and format the lines properly as suppose to doing it when you /write since this has a 950 or so character limit.
Best method would be to use the
getElementsByTagName in conjunction with Javascript timers and XMLHTTP requests to your .txt file and only load in the new lines without page refreshes.
As always im just rambling on and spitting idea's but this is very plausible.