You have a 3rd party plugin installed that has not been updated for Elgg 1.8 yet. You should be able to find out which plugin is responsible by removing the widgets on your profile page until you found the one resulting in the error.
I also was very confused when I first saw this error message. Basically, the expected file name for the widget code php file changed from "view.php" to "content.php". Of course there are other things you might to upgrade for the plugin but by renaming the widget source code file the above message should vanish.
You should tell the developer of the plugin about it.
Honestly don't even know which widget it is, because I don't see anything but that error code. Now gotta go one by one to find out.
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