The solution to no "tree mode" menu

[greggy]

Cacti Version: 0.8.8f
OS Version: Deb 8.2
Problem: The "tree mode" is blank ie. no menu shows (see exhibit 1)
Reason: The tree mode view is loaded by a javascript, if it does not load then your problem is related to javascript -- not Cacti.
Approach: The thing to use for troubleshooting javascript is a web browser. Here the browser of choice is firefox because it has an addon tool called "firebug" that will show us what is going on with javascript.

1) Install the addon firebug; then launch it - click on the bug icon in the top right hand corner of browser. (see exhibit 2)
2) When firebug is launched click on Net menu and javascript submenu. (see exhibit 3)
3) In the javascript submenu focus on items in "red" and look at the status column - it will give you what needs to be fixed. (see exibit 4)
4) Click one of the items in red (the plus sign under URL column to expand) then navigate to the html column. (see exhibit 5)

Conclusion
Here you see that (in this case) the root cause of the problem is that the javascript jquery is unable to execute against cacti because javascript is not running as a web site.

The fix
Find your javascript installation and add it to apache.
1) For debian: enter at the shell#whereis javascript -- it should answer that it is at /usr/share/javascript
2) For debian: edit /etc/apache2/apache2.conf and add the lines in exhibit 6 and restart apache (service apache2 restart for debian).

Now you should see your tree mode menu. (exhibit 7)