Can't access CS3 download, getting 404 Error.

This worked for me:

1) Goto the link to download your product.  COPY the link to a text program somewhere.  For example, for Photoshop CS3: http://esd.adobe.com/Applications/Photoshop/CS3/Mac/ADBEPHSPCS3_WWE.dmg.

2) Now click the link, in an attempt to download.

3) When you get the error message, paste the link you copied into the URL but DON'T hit enter or navigate to it yet.

4) Change the link to the Trials2 url. For example: http://trials2.adobe.com/dlm/Applications/Photoshop/Mac/ADBEPHSPCS3_WWE.dmg

You are essentially changing the "esd" to "trials2" and adding "/dlm" before "Applications".  This worked for me!

I could not go to the link directly, and if I paused the download and restarted, it said I didn't have permission.  It appears to have to goto the error message screen FIRST, then paste in the modified download link and you should be good to go!

use a different browser.

or if you follow all 7 steps, you can download a trial via one of the links on this page using a browser that accepts cookies:  Download Adobe CS4 and CS3 Free Trials Here (incl. After Effects) | ProDesignTools

and activate with your serial number.

if you have a download problem (eg, you see an error page or you are offered an incorrect version), you probably didn't follow all 7 steps.  typically, failure to meticulously follow steps 1,2 and/or 3 is the problem, but your browser must also allow cookies so that (a restrictive browser setting) is another potential source of problems.