You only need to remove all the trust bits via the Edit button in the Certificate Manager to prevent Firefox from using the certificate as root certificate.

That should have happened when you updated to Firefox 6.0.2

thanks cor-el i use Firefox 6.0.2 and in about window FF say you are update i deleted this ca several time.. but in my CA section i see new DigiNotar CA certificate installed without any warning message or somethings like CA error or any question... is this new CA is true and safe  ?

You can NOT remove the certificates. They have been de-activated.

Go to Options > Advanced > Encryption > View Certificates. Scroll down to DigiNotar, the certificates for each item listed under the DigiNotar heading should have all items un-checked when you click "Edit Trust" for each of the listed certificates. Do not make any changes. You can compare to other certificates, other the DigiNotar, by clicking "Edit Trust" on them; some will have one or more of the 3 items checked.

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Not related to your question, but...

You may need to update some plug-ins. Check your plug-ins and update as necessary:

• Plug-in check: https://www-trunk.stage.mozilla.com/en-US/plugincheck/
• Adobe Shockwave for Director Netscape plug-in: Installing (or Updating) the Shockwave plugin with Firefox
• Adobe PDF Plug-In For Firefox and Netscape: Installing/Updating Adobe Reader in Firefox
• Shockwave Flash (Adobe Flash or Flash): Updating Flash in Firefox
• Next Generation Java Plug-in for Mozilla browsers: Installing or Updating Java in Firefox

Select a DigiNotar certificate in the Certificate Manager.

• Click the Edit button to verify that all trust bits are unchecked
• Click the View button and go to Details to verify that the certificate has been deactivated (Explicitly Distrust DigiNotar Root CA)