Are All The Programs Listed In Major Geeks Tested So They Can Be Safely Downloaded?

There are an incredible number of programs listed om Major Geeks. Can users be sure if a few of them are downloaded, they are safe and won't cause any problems if used correctly??

 

That's not really anything to do with individual programs themselves. They are all tagged with what operating systems they are tested for use on.
It's the system they are installed on and their compatibility with any other programs also installed on the same system that you probably mean. Every system is unique to a user and what they do with it. If you as a unique user experience any system problem with any one or more programs, you need to start an appropriate thread in the Software forum.

 

All the programs hosted by MajorGeeks have been tested by the owners.
They are malware free.

Look at License:
Freeware, Shareware $, Open Source or Ad-Supported.
Have a look over here:
http://www.majorgeeks.com/content/page/what_is_ad_supported.html

Whether they will cause problems even when correctly used?
The short answer is No.
However, take care when using tweaking/optimizing programs.
And...