check this:

• see if there are updates for your graphics drive drivers

https://support.mozilla.org/kb/upgrade-graphics-drivers-use-hardware-acceleration

• disable protected mode in the Flash plugin (Flash 11.3+ on Windows Vista and later)

https://forums.adobe.com/message/4468493#TemporaryWorkaround

• disable hardware acceleration in the Flash plugin

https://forums.adobe.com/thread/891337 See also:

• http://kb.mozillazine.org/Flash#Troubleshooting

Start Firefox in Safe Mode {web Link} by holding down the <Shift>
(Mac Options) key, and then starting Firefox. Is the problem still there?

Thanks for the reply @FredMcD, I followed your recommendations however none of these helped.

• My graphic drivers are up to date, issue still present
• Hardware acceleration is turned off, issue still present
• I've disabled WebGL, issue still present
• Flash is disabled (Ask to Activate) and protected mode is not available for OSX. Furthermore, this issue happens on pages with no Flash at all.
• Flash hardware acceleration is disabled, issue still present
• Started Firefox in Safe Mode, issue still present
• Completely uninstalled Firefox and performed a clean install, issue still present

sebasll said

• Started Firefox in Safe Mode, issue still present

This means the problem may be outside Firefox.

Type about:addons<enter> in the address bar to open the Add-ons Manager. Hot key; <Control>(Mac:<Command>) <Shift> A)

On the left side of the page, select Plugins. Make sure the ones you want to use are set to Ask or Allow.

Go to the web page. Once the page is loading, mouse to the address bar and Left click the icon. A window for displaying site information should come up. Select More Information. Now select Permissions. In the menu, Make sure the ones you want to use are set to Ask or Allow.

Use this link to check that your plugins are up-to-date. If any are listed as unknown or research, do not worry about them.

https://support.mozilla.org/en-US/kb/websites-look-wrong-or-appear-differently

https://support.mozilla.org/en-US/kb/fix-common-audio-and-video-issues?redirectlocale=en-US&redirectslug=Video+or+audio+does+not+play

https://support.mozilla.org/en-US/kb/fix-common-audio-and-video-issues

Thanks, but not sure how my plugin permissions are related to the artifacts that I'm seeing on all websites. None of the plugins are related to display rendering.

All my plugins except for the default Firefox OpenH264 plugin are set to Ask to Activate. Once set here, I shouldn't have to do this on a page per page basis, unless I want different rules for that particular page. Nevertheless I did test it and Issue is still present.

All plugins are up to date as well.

Is the issue with one site, or several?

Start your Computer in safe mode with networking. Then start Firefox. Try Safe web sites. Is the problem still there?

Starting The Computer In Safe Mode;
Free Online Encyclopedia

Many site issues can be caused by corrupt cookies or cache.

• Clear the Cache and

• Remove Cookies
  Warning ! ! This will log you out of sites you're logged in to.

Type about:preferences<Enter> in the address bar.

• Cookies; Select Privacy. Under History, select Firefox will Use Custom Settings. Press the button on the right side called Show Cookies. Use the search bar to look for the site. Note; There may be more than one entry. Remove All of them.
• Cache; Select Advanced > Network. Across from Cached Web Content, Press Clear Now.

If there is still a problem, Start Firefox in Safe Mode {web link} While you are in safe mode;

Type about:preferences#advanced<Enter> in the address bar.

Under Advanced, Select General. Look for and turn off Use Hardware Acceleration.

Poke around safe web sites. Are there any problems?

Then restart.

Since zooming, which forces a repaint, fixes the display at least temporarily, you could try disabling OMTC, a feature introduced in Firefox 33. Here's how:

(1) In a new tab, type or paste about:config in the address bar and press Enter. Click the button promising to be careful.

(2) In the search box above the list, type or paste layers and pause while the list is filtered

(3) Double-click the layers.offmainthreadcomposition.enabled preference to switch it from true to false

Any difference?

Note: I read in a bug report a while back that this change causes problems with the HTML5 player on YouTube, if hardware acceleration is disabled, so you might also need to force Flash on YouTube if you keep this setting. You can use an add-on for that: https://addons.mozilla.org/firefox/addon/youtube-flash-video-player/

OMG, jscher2000, thank you so much. That totally fixed the issue that I was having. Odly though it only started happening when I updated from Frirefox versoion 38 to 39. It also seemed to affect the browsers UI components (toolbar, titlebar, etc.) It was driving me nuts.

Firefox should really look into this issue.

As far as YouTube, I only use the HTML5 player, so I have no concerns there. Even if I did, I much rather have a properly working browser.

Anyhow, thanks again jscher2000