Hi alecsus27,
the web page that's opened through cardtricks only contains "official" builds. As the version for the a590is is still in beta stage (although ma_jk has improved it at an unbelieveable speed during the last days), it's not there - yet.
You can skip the "download CHDK" step in cardtricks and instead load the version appropriate for your firmware here:
A590IS porting...Once downloaded, you can use "CHDK -> card" in cardtricks and choose the archive you just saved. Cardtricks will then unzip it to your card. That's it, lock the card and place it into your camera.
For reference, your card should at least contain 'diskboot.bin', 'ver.req' and 'vers.req' in it's root folder now, plus a 'CHDK' folder in which there are several other subdirectories like 'Books', 'Curves' etc..
If you have the correct firmware, and cardtricks says the card is bootable (beginning with 4GB+ you might run into problems, I've heard), it should work.
Are you sure you have the correct version for your firmware? 100e and 101b are not referring to the build, but to your camera (see
here).
HTH,
Cyro
Edit: damn, I should try writing less lengthy - sorry whim, didn't mean to repeat you

Edit2: according to reply #156, it's possible to get it working on a 4GB SDHC card. According to
Wikipedia, it's possible to access cards bigger than 2GB (the design limit of standard SD cards) through the standard SD interface (which seems to be needed for booting CHDK), but you can't be sure, as this would be outside the standard.