Which are the different automation testing (software testing) tools which are available in the market? Also, with the emergence of various automation testing tools in the market, will the demand for manual testers reduce considerably in the future?

The most common type of error that we see is error 404. Can someone explain to me what exactly it is and why is it so common? Is this an error caused because of some fault at the client-side or server-side?  

Can someone explain to me what bad Gateway error means and why does this happen? Is it a client-side error or a server-side error and would it cause any problem in the network?

Can someone explain to me what does the error 504 mean and how it can be fixed? Is this error caused because of the Client or the server?

Can someone explain to me why a system crashes, and the error message is displayed along with it in a blue screen especially for a Windows operating system and the various way how a system denotes this crash?

I have a Windows PC, and recently I had got an error message on my computer saying that a fatal exception has occurred along with some code and my computer shut down unexpectedly. Can someone explain what went wrong and how to solve this problem?

I use Windows PC recently I get a device error when I try to use my USB. But the USB works fine when I use it on another computer. So what is the problem here, and how can I resolve it?

I have a Windows 10 PC, and sometimes I get missing DLL files for a few programs that access system files. Can someone explain to me what a DLL file is and how I can correct this error?

I have a Windows PC, and I came across virtual memory too low. Can someone explain what virtual memory is and why I am getting this error and how to fix it?

I have heard system32 error is the most common type of error that one can get in a Windows operating system, yet it is the most dangerous of all the errors. Can someone throw light on what it exactly is a system 32 error and how to fix it?