I had it preventing me access a site using an android app once. I think that the app must have been refusing to continue to the site until I acknowledged the full page ad that I could no longer see.
I'd start with ummmm's answer before worrying about digging all the details of your computer and its operating system. It's a very straightforward process if you can find the red hand symbol
Mine is same as hc's.
Mine is located along the bottom - if you can't see it, it's prob because you haven't got he "status bar" highlighted. Right click on the menu bar along the top and make sure there's a tick next to the "status bar".
@hc4361...I am sorry having to disagree with you when you say " The make/model, operating system and browser of your pc is irrelevant to this problem."
The position of the the Adblock icon can vary on the desktop (screen) and colour and format can differ. Obviously you have Adblock Plus but some Browsers can only accept ordinary Adblock: hence a Red Hand and Not the letters ABP. Anyone using Safari as a Browser will have a White Hand in a Black Octagonal.
At the moment I am waiting to see of henry posts further on this matter.
Strange that you are still unable to contact the website.
I feel sure that, if you disclosed the name of the actual site, there could be a Techie in Answerbank who would be able to resolve your problem. There are means by which it can be established if a site is still 'Up & Running'.