3rd Party Counters

I have been building a search engine for about 9 months now of links to
other site that I have admin Access to. This has been simple for me to keep
mySQL record of page hits, as I admin all the sites.

I now have a requirement to add 3rd party pages, that require to be able to
increment counters tables on mySQL database.

This is exactly the same requirement as other 3rd party counter web sites
offer. They seem to do it with a bit of java and an image. Unfortantly I
have no idea how it is done..

each of my search engine records has a unique ID, --------- :-)

I just want for example when a 3rd party page is loaded, for it to HTTP GET
the image from my server and somehow know carry the unique ID for the
record, so when my server receives the HTTP GET for the particular image or
Javacode it can translate the sent varable so that I know what counter to
update..

This seemed easy the more I thought about it, the more I realized I did not
have a clue how to do it... The only thing is that it must not be ASP on the
client as I am not sure all of my 3rd party links have ASP. So I suppose it
must be javascript based..