Sometimes the one-pixel image is a substitution made by the "Anti-Banner" feature in Kaspersky products. If you use Kaspersky, could you try disabling that feature?

You can check the Web Console (Tools -> Web Developer) for messages about blocked content and about the presence of mixed or unsafe content. *https://developer.mozilla.org/en/Tools/Web_Console You can check the Network Monitor to see if content is blocked or otherwise fails to load. *https://developer.mozilla.org/en/Tools/Network_Monitor Use "Ctrl+F5" or "Ctrl+Shift+R" to reload the page and bypass the cache to generate a fresh log. ---- You can try these steps in case of issues with web pages: You can reload web page(s) and bypass the cache to refresh possibly outdated or corrupted files. *hold down the Shift key and left-click the Reload button *press "Ctrl + F5" or press "Ctrl + Shift + R" (Windows,Linux) *press "Command + Shift + R" (Mac) Clear the cache and remove the cookies from websites that cause problems via the "3-bar" Firefox menu button (Options/Preferences). "Clear the cache: *Options/Preferences -> Privacy & Security -> Cached Web Content: "Clear Now" "Remove the cookies" from websites that cause problems. *Options/Preferences -> Privacy & Security -> "Use custom settings for history" -> Cookies: "Show Cookies" Start Firefox in <u>Safe Mode</u> to check if one of the extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) or if hardware acceleration is causing the problem. *switch to the DEFAULT theme: "3-bar" menu button or Tools -> Add-ons -> Appearance *do NOT click the "Refresh Firefox" button on the Safe Mode start window *https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode *https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems