Warning message in Lion

Question

Hi ,
I just installed Mac OSX Lion.
When I download a set of images (like a manga for example) in Preview , a warning message saying that this is an image taken from the internet (and asking me if I'm sure I want to open it) keep bugging me. How to get rid of this message ?
Thanks to thoses who could help me.

Answer 1

Does it say "image" or application
Protect your computer from harmful applications
Some harmful applications exist that can cause problems for your computer. Frequently, a harmful application will try to appear as an innocent document, such as a movie or graphic file. These applications, called “trojans,” are most often spread by Internet downloads and email enclosures.
Important: If you receive an application warning and you don’t expect the file to be an application, don’t open the file. Delete it from your computer. 
Here are some tips to protect your computer from harmful applications.
Never download unlicensed or “pirated” software from the Internet.
Accept only applications you receive from a known and trusted source.
Run an antivirus program if you find any suspicious files or applications, or if you notice any suspicious behavior on your computer.
To reduce the amount of exposure to harmful applications or files, limit the number of administrator accounts you create. Consider creating a user account for your daily work and use the administrator account only when you need to install software or administer accounts.
If you enabled the root user and you don’t currently need it, disable it.