Is selleckchem.com a virus?

Hi everyone!!!!There's something strange on my Mac...Every page I'm going to visit on internet has this site as advertising...www.selleckchem.com...I'm not a doctor or medicine interested....but it's not possible..in every single page I'm visiting...I found this adv...

Is it possible It s a malware, trojan or a virus???I launched Viruss barrier, and I antvirus...they didn't find anything

any suggestion??

thank you all