go to Help Menu -> select "Restart with Add-ons Disabled"

Firefox will close then it will open up with just basic Firefox. Now do this:

-> Update ALL your Firefox Plug-ins https://www.mozilla.com/en-US/plugincheck/

-> go to View Menu -> Zoom -> click "Reset"

-> go to View Menu -> Page Style -> select "Basic Page Style"

-> go to View Menu -> Toolbars -> unselect unwanted toolbars

-> go Tools Menu -> Clear Recent History -> Time range to clear: select EVERYTHING -> click Details (small arrow) button -> place Checkmarks on ALL Options -> click "Clear Now"

-> go to Tools Menu -> Options -> General -> When Firefox starts : select "Show My Home Page" -> Type the address of the website which you want to be your HomePage e.g. http:www.google.com -> click OK

-> click the Favicon (small drop down menu icon) on Firefox SearchBar (its position is on the Right side of the Address Bar) -> click "Manage Search Engines" -> select unwanted search engines and click Remove -> click OK

-> go to Tools Menu -> Add-ons -> Extensions section -> REMOVE any Unwanted/Suspicious Extensions (Add-ons) -> Restart Firefox

You can enable your Known & Trustworthy Add-ons later. Check and tell if its working.

Which encoding is selected on pages where you see this?

• Firefox > Web Developer > Character Encoding

Can you post a link?

Unicode.

You may need a Western encoding like Western (ISO-8859-1) if characters are missing or you see question marks.

Clear the cache and the cookies from sites that cause problems.

"Clear the Cache":

• Tools > Options > Advanced > Network > Offline Storage (Cache): "Clear Now"

"Remove Cookies" from sites causing problems:

• Tools > Options > Privacy > Cookies: "Show Cookies"