This software tool provides a translation in the form of a tool-tip or "speech bubble" that appears above words in the text of web-pages. This occurs when the word is hovered over and therefore the text can be read with translation help when needed.
Translation of highlighted or selected text is also provided in the tool-tip so that the context of the word can aid with understanding of the sentence.
39 languages are supported from Arabic (العربية) to Vietnamese (Tiếng Việt). Text to speech technology also allows you to hear the word(s) as audio.
You can also use the vocaPOP extension as a screen reader, just select your native language for the 'from' and 'to' options and the 'audio' radio button option and any text on the page will be read to you on hover or select.
As Firefox now interprets PDF files as html you can also use the tool to translate PDF files hosted on the web. More information and a demonstration can be found at vocapop.com.
It could be that the service has reached the limit of free translations. If you find the application useful and don't want to be limited then please contact me via support email.