Here are a few steps you can try to resolve the problem: '''Update Firefox''': Ensure you are using the latest version of Firefox. Sometimes, updating the browser can fix rendering issues. '''Disable Hardware Acceleration: ''' * Open Firefox and go to the menu (three horizontal lines in the upper-right corner). * Select "Settings". * Scroll down to the "Performance" section. * Uncheck "Use recommended performance settings" and then uncheck "Use hardware acceleration when available". * Restart Firefox and see if the issue persists. '''Clear Cache and Cookies:''' * Go to the menu and select "Settings". * Navigate to "Privacy & Security". * Under "Cookies and Site Data", click "Clear Data". * Check "Cookies and Site Data" and "Cached Web Content" and click "Clear". '''Try Safe Mode:''' * Start Firefox in Safe Mode by clicking the menu button, selecting "Help", and then "Restart with Add-ons Disabled". * If the problem doesn't occur in Safe Mode, an extension might be causing the issue. You can then disable extensions one by one to identify the culprit. '''Reinstall PDF Viewer Plugin:''' * Bulleted list itemIf you're using a third-party PDF viewer plugin, try reinstalling it or switching to a different one.