The problem you are experiencing is a freezing of that program, the "clouding over" effect is either a temporary lockup of the programs internals or it is the death throws of the current instance of the program.
When it disappears from the screen that means the program did something that it should not do and the operating system (the computer) decided to terminate the Program and it's Window.
You can of course restart the program but the chances are it will do the same thing again.
From your earlier responses I am pretty sure you are only using the computer for Browsing so I doubt you have many other programs installed, so chances are that it is just your Browser that is acting up.
I use multiple browsers both Internet Explorer and Google Chrome and recently I have found that Internet Explorer has been pretty flaky, Microsoft sometimes make things worse rather than better when they release "fixes" that get automatically installed on your computer.
I am guessing from what you have said that you are using Microsoft's Internet Explorer if you are still having problems the easiest thing to do would be to install another Browser and as Keith recommends Firefox you should go with that.
All Browsers and indeed all programs can crash like this, it is ultimately always the fault of a programmer like me somewhere
occasionally it can be the hardware at fault but it's usually the programmer
Jim