I was just reading an article this morning (see link below) that was geared around the Top Ten Security tips that every developer must know, as the title states. I am not sure that these are the "TOP 10" or not, but I think that they are all pretty good (Especially #4, IMHO), so I am sharing.
(Example of #4...Bad Developer...bad developer)
If you want to add to this list, please feel free to post in the response section of this blog.

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Here's the list:
- Trust User Input at Your Own Peril
- Protect Against Buffer Overruns
- Prevent Cross-site Scripting
- Don't Require sa Permissions
- Watch that Crypto Code!
- Reduce Your Attack Profile
- Employ the Principle of Least Privilege
- Pay Attention to Failure Modes
- Impersonation is Fragile
- Write Apps that Non-admins Can Actually Use!
To see the full article (Written by: Michael Howard and Keith Brown): Click here
~Robert Shelton