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After resetting Firefox, LCD screen has lost some of its sharpness - like there are pixels missing - WHY?

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I have a PC running Windows 7 Ultimate. Lately when I am in Firefox (running most current version), if I try to open more than one tab, Firefox slows down and I get the message "Mozilla Firefox not responding"; within a few seconds whatever site I am trying to open in the new tab opens; Firefox just seems to be sluggish. I finally tried resetting Firefox. After I did the reset, I noticed that the images on my monitor (Acer LCD S200hl) seemed to be less clear, even the wallpaper. As I type this, there appear to be holes in the image on screen, as if pixels are missing. Some of the letters look as if they are not completely filled in. The only change is that I reset Firefox. Any help will be appreciated.

I have a PC running Windows 7 Ultimate. Lately when I am in Firefox (running most current version), if I try to open more than one tab, Firefox slows down and I get the message "Mozilla Firefox not responding"; within a few seconds whatever site I am trying to open in the new tab opens; Firefox just seems to be sluggish. I finally tried resetting Firefox. After I did the reset, I noticed that the images on my monitor (Acer LCD S200hl) seemed to be less clear, even the wallpaper. As I type this, there appear to be holes in the image on screen, as if pixels are missing. Some of the letters look as if they are not completely filled in. The only change is that I reset Firefox. Any help will be appreciated.

Chosen solution

In case it's an incompatibility between Firefox and your graphics card driver, try disabling Firefox's use of hardware acceleration. You might have done this once before, but of course, the Reset turns it back on.

orange Firefox button (or Tools menu) > Options > Advanced

On the "General" mini-tab, uncheck the box for "Use hardware acceleration when available"

This will take effect after you exit and restart Firefox. Any difference?

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Chosen Solution

In case it's an incompatibility between Firefox and your graphics card driver, try disabling Firefox's use of hardware acceleration. You might have done this once before, but of course, the Reset turns it back on.

orange Firefox button (or Tools menu) > Options > Advanced

On the "General" mini-tab, uncheck the box for "Use hardware acceleration when available"

This will take effect after you exit and restart Firefox. Any difference?

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That was it - problem solved - thank you!