& as I didn't have a clue, I did some research. I'm not sure what's relevant & what's not, & I wouldn't blame you if you ticked this as resolved soon as you read this lot!
Apparently the browser add-ons are marked as "Not verified" as they haven't (yet} been 'digitally signed' by the publisher.
From click here - "A signed add-on contains a digital signature. A digital signature is data that binds a sender's identity to the information that is sent."
Also, watch this short video on the IE Add-ons Manager click here (Flash Player required).
I don't think there's a way to 'verify' these files/programs as they're not digitally signed in the first place (but I may be wrong). (To verify a digitally-signed program I think you'll need something like click here).
Don't worry about the unverified ones. If you're ever in doubt ask here or do a search on Google. Fortunately they can be disabled, & hopefully easily removed. G
About Digital Signatues (DS) from click here - "When software (code) is associated with a publisher's unique signature, distributing software on the Internet is no longer an anonymous activity. Digital signatures ensure accountability, just as a manufacturer's brand name does on packaged software. If an organization or individual wants to use the Internet to distribute software, they should be willing to take responsibility for that software. This is based on the premise that accountability is a deterrent to the distribution of harmful code." (More details on DS click here)
Using the File Signature Verification tool (FSV) (from click here - "To check the digital signatures for system or non-system files"), scanning my PC in C:\Program Files (incl subfolders), I found 9951 (of 10,480) that are NOT digitally signed. A search in C:\Windows (incl. subfolders) found 6201 (of 18,555) files that are not digitally signed. Apparently only critical files need to be digitally signed - see the statement in the FSV tool dialogue box.
For anyone wondering how to access the browser add-ons list, watch the short video - link above, or in IE go to Tools>Internet Options>Programs & click the 'Manage Add-ons' button (may only be present in WinXP & IE6).