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Remove the following to the trash and restart the computer and try again:
Home > Library > Caches (I remove the whole folder. It will be re-generated upon restart.)
Home > Library > Preferences > com.apple.iweb
If the issue persists there may be something wrong with your domain file (where iWeb stores your website). This error sounds like a permissions issue.
_Go to Home > Library > Application Support > iWeb and rename the "Domain" to "DomainOld"
_Launch iWeb and make a new page (This is a new Domain so you will not see anything you have created thus far)
_Make a change to the page like adding some text and then quit and save iWeb -- See if you get the error message
_If you do not get the error message then something is wrong with your original Domain file.
_If you don't care about what is in that Domain so far just keep using this new one.
_If you want to keep using the original Domain you can try getting rid of the new "Domain" found in Home > Library > Application Support > iWeb and renaming the "DomainOld" back to "Domain".
__Double-click that Domain and see if it will open and allow you to make changes.
Hope that helps.
