... Thats someone having a problem with being given an incorrect certificate for a website because their ISP was blocking the website they were trying to access. Even though its on a linux support forum its neither a linux nor firefox issue.
If you read the thread they were using google dns to get around ISP blocks. They had set it up for ethernet but not for wifi (i presume they had already set it up fpr windows). Not using the service you want but havent set up is not an OS problem.