Never ignore a certificate warning\!
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If a program complains about an incorrect certificate of e.g. a website, then never ignore this, but report this to C&CZ a.s.a.p.. The reason to give this warning is a recent complaint of a browser, that pointed to a contaminated laptop, that launched an ARP spoofing attack. The idea behind such an attack is to listen to network traffic in order to e.g. obtain passwords.