3/ from your screenshot, it looks like the user is on a mobile device. One of your ads is probly animated with Adobe Flash (swf). Since the users mobile browser has no clue what the file is, it's trying to download it for him, rather than run it.
just take a look at your site and see some strage urls blocked by my adblocker. Are you sure to use only static gilf files for advertisment? If I enter your site my adblock tells me connections to: britbike.com adzerk.net ajax.googleapis.com bufferapp.com cloudflare.com d1zoyh6qfvajy7.cloudfront.net dsms0mj1bbhn4.cloudfront.net ebay.com facebook.com fancy.com fbcdn.net fonts.googleapis.com google-analytics.com gstatic.com napaliprop.com ok.ru pinterest.com ravenjs.com reddit.com shareaholic.com tumblr.com viglink.com vk.com yummly.com
The reported .swf (flash file) can be a malware. Check your server for modified .htaccess files. The name of the file looks like dynamic generated. The browser don't support Flash anymore and display the unknown extentions for donwload. This is releated to the browser of the client. But you have to find out where it comes from: your server, your ad's or a malware injection on client side.
In PC browsing with Firefox no .swf shows up on my side. It can be a injection to mobile browsers only. This can be detected by scripts.
I have searched for anything starting with "Rzk" as in the .swf file on my server but nothing appeared.
These are known on britbike.com britbike.com ebay.com facebook.com pinterest.com shareaholic.com google-analytics.com --------------- Have just installed - cloudflare.com --------------------- Have no clue what below is...- adzerk.net ajax.googleapis.com bufferapp.com d1zoyh6qfvajy7.cloudfront.net dsms0mj1bbhn4.cloudfront.net fancy.com fbcdn.net fonts.googleapis.com gstatic.com napaliprop.com ok.ru ravenjs.com reddit.com tumblr.com viglink.com vk.com yummly.com