Viagra ads popping up, affecting google resutls

Dunno where I should put this, so this seemed a good of a place then any.

Recently we have had a visitor to our site get in contact saying we have viagra ads on our website. I had a look on many browsers, on multiple systems and got nothing, thinking they must have some adware of somesort doing this on there specific machine.

However I recently managed to search for the following in google:
https://www.google.co.uk/search?q=site%3Ainhalefashion.com+viagra&oq=site%3Ainhalefashion.com+viagra&sugexp=chrome,mod=0&sourceid=chrome&ie=UTF-8

And found that infact, there are words in our site with the word: viagra.

Is there anyway someone could have maliciously inserted these into my website? Even though I cannot see these ads at all?

Any help would be great.

Regards,
Joe.

Just some questions:

- On what platform are you providing your site? Blogger, Wordpress, Joomla, etc.
- Are you hosting it by yourself or in some other hosting site?
- If not developed on any major platform, are you coding the site yourself?
- Does it uses Mysql/Php interaction with the user? (This may be a 'hot spot' for our trouble here).

If you're hosting it by yourself, please let me know and hand to me as many details as you can from your enviroment (OS used, Server used - Apache, Lighttpd, Nginx, Jigsaw, etc).

Looking forward to assist you.

It sounds like that is exactly what has happened.