cannot read Help Topics
CHM files downloaded from a website cannot be viewed
Due to excessive caution on the part of some Windows systems
you may get an "Action cancelled" message on opening a CHM
file which you have downloaded from a website.
The work around is as follows. In Windows Explorer, right
click on the CHM file name and select Properties.
Click "Unblock" and "Apply".
"This program cannot
display the webpage"
Help files not displayed
correctly across a network
When viewing CHM files (WALLAP, SLOPE or GWALL Help), you
may see the message:
"This program cannot display the webpage"
If the Contents displays OK, but the help text does not,
then you are probably viewing your CHM file over a network.
Microsoft in its wisdom decided that CHM files were a
security risk because you can embed ActiveX's, external
links to exe's etc. So, they released a Windows Critical
Update, KB896358, which effectively means that CHM files
can not be viewed on a network shared folder.
This problem applies to all CHM files on a network. If you
view the CHM file from your local disk, i.e. the C drive,
it will display as expected.
Geosolve has attempted to solve this problem by getting
WALLAP to make a copy of the CHM file on your local Hard
Disk. If the problem persists then you should implement the
The solution is to add a MaxAllowedZone registry value and
to set it to at least 1, as this permits access to HTML Help
files stored both locally (Local Machine zone) and remotely
(Local intranet zone). In case that is something you donít
feel entirely comfortable with there is a handy utility which
you can download from
If you want to apply this fix, open the zip file and double-click
the reg file and the setting will be added to your Registry. This
needs to be done on each workstation that access CHM files on
Revised December 2019