Hymer, the thumbnails are on a separate page called thumbs.htm which is being loaded into an iframe on the start page called 'mythumbs'. This is fine - but you are trying to tell the browser to open the links referenced to each thumbnail into an <iframe which is NOT on the thumbs page but on the start page, the result is that the referenced page is opening inside the same iframe because there is no-where else it can. You cannot tell one remote page to open another .htm file into a frame inside another remote page. The browser doesn't know where the iframe named 'myframe' is because thumbs.htm has no iframe named 'myframe' - it's on the start page (which by the way you have named chilenska.htm - so won't load by default on a web server unless you specify this name in the URL - you should leave it as index.htm)
Basically, you have got yourself into a bit of a muddle
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