HTTP ERROR: 404 /support/downloads/dlm/main.jsp

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!

Incidentally, this file appears to be the same file linked to from:

http://prodesigntools.com/download-adobe-cs4-and-cs3-free-trials-here.html

with prodesigntools.com, you must follow the instructions on the download page.

Downloads available:

• Suites and Programs:  CC 2014 | CC | CS6 | CS5.5 | CS5 | CS4 | CS3
• Acrobat:  XI, X | 9,8 | 9 standard
• Premiere Elements:  13 | 12 | 11, 10 | 9, 8, 7 win | 8 mac | 7 mac
• Photoshop Elements:  13 |12 | 11, 10 | 9,8,7 win | 8 mac | 7 mac
• Lightroom:  5.6| 5 | 4 | 3
• Captivate:  8 | 7 | 6 | 5
• Contribute:  CS5 | CS4, CS3

Download and installation help for Adobe links

Download and installation help for Prodesigntools links are listed on most linked pages.  They are critical; especially steps 1, 2 and 3.  If you click a link that does not have those steps listed, open a second window using the Lightroom 3 link to see those 'Important Instructions'.