How can you determine that the website is free of malwares?

i dont know of anyways to recognise the infected sites. the best thing to do would be to strengthen the security of your pc. install anti malwares, antispywars,antivirus and then browse without any worries ;) and in some sites it automatically prompts whether to install a particular plugin or such ,dont choose to install. just cancel it,most of such stuffs are infected. try to install whatever from official sites.