Looks like a broken help file, right? But it's not - it's merely a Windows security 'feature' that tries to be overly helpful in protecting you. If you look at the URL of a help topic you see something like this:. Try pasting a URL like this into Internet Explorer and you'll see the help topic pop up in your browser along with a warning most likely. Although the URL looks weird this still equates to a call to the local computer zone, the same as if you had navigated to a local file in IE which by default is not allowed.
Unfortunately, unlike Internet Explorer where you have the option of clicking a security toolbar, the CHM viewer simply refuses to load the page and you get an error page as shown above. Clicking the Unblock button basically, tells Windows that you approve this Help File and allows topics to be viewed.
Is unblocking insecure? In recent versions of Windows Internet Explorer pops up various security dialogs or fires script errors when potentially malicious operations are accessed like loading Active Controls , so it's relatively safe to run local content in the CHM viewer. Since most help files don't contain script or only load script that runs pure JavaScript access web resources this works fine without issues.
As an application developer there's a simple solution around this problem: Always install your Help Files with an Installer. The above security warning pop up because Windows can't validate the source of the CHM file. However, if the help file is installed as part of an installation the installation and all files associated with that installation including the help file are trusted.
A fully installed Help File of an application works just fine because it is trusted by Windows. It's annoying as all hell that this sort of obtrusive marking is necessary, but it's admittedly a necessary evil because of Microsoft's use of the insecure Internet Explorer engine that drives the CHM Html Engine's topic viewer. Because help files are viewing local content and script is allowed to execute in CHM files there's potential for malicious code hiding in CHM files and the above precautions are supposed to avoid any issues.
Ad-free experience sponsored by:. Share on:. On this page:. Is this content useful to you? Consider making a small donation to show your support. Darren Stokes December 28, I had this problem several months ago and I would hit the unblock button and press ok and the file was still blocked. I eventually noticed the file was read-only.
After clearing the read-only flag and pressing apply, the unblock worked. Jay January 04, I see what you describe above. The software has been installed from disk and not downloaded from the Internet. I usually copy the file to my desktop in order to be able to read it! Richard Deeming January 05, I got so fed up with it that I wrote a utility to recursively unblock all files in a particular folder.
Daniel Fernandes January 17, Rick Strahl January 17, The format is not a problem - it's Microsoft's unwillingness to update or fix it for the last 10 years. As you can tell this is one topic that REALLY pisses me off and shows another area where a total lack of competition or incentive leaves Microsoft just not giving a shit.
Thanks so much. Howard January 31, Brenda February 17, At the bottom of the General tab is Attributes and is the last thing on that window. Is there another way to unblock it?
LadyE February 22, Drayton February 23, CHM that reside on a server share to be displayed. The user will be able to see the TOC Table of Contents but does not allow the actual content to be displayed. The help file can be displayed will all content if the help file is on the local machine that is useing the application. Here is a quick work-around that will enable the users to see the complete help file regardless. The CHM file has to be located in the same directory as the database that is to use it as a help file.
Name, Len CurrentDb. Name - Len Dir CurrentDb. Jamie March 03, I wish I would have found this before I did a write up on it on my blog. You are trying to open a CHM file but get a message like "Navigation to the webpage was canceled" or "This program cannot display the webpage" instead of the topic content.
Here are the reasons why that can happen:. Type in the following to your command prompt: "regsvr32 hhctrl. After getting the success message like "DllRegisterServer in hhctrl. Hash is a registered character which is used for hyperlinks. This character can not be used as well as "? All those have special meaning. Submit ». Get answers from your peers along with millions of IT pros who visit Spiceworks. Microsoft Windows 10 Pro Microsoft Windows 10 Adam AJ Tek This person is a verified professional.
Verify your account to enable IT peers to see that you are a professional. I've seen that before, I just presumed it was crappy help files. Steve Regrettably, I am not seeing the checkbox for the Unblock of the.
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