Totally blank blog after Flickr upload!

Please help me with this one!

I successfully set up Flickr to work with my blog, but when I changed some of the code of the upload-template in Flickr, and uploaded a photo to my blog using this modified code, I just got a blank page. I can’t even access the admin page of my blog – It’s all blank. No 404 error, just a blank page.

Here’s the code from the Flickr-upload template that I used to upload the last post before everything went blank:

<a href="https://www.flickr.com/photos/26382484@N00/1507140417/" title="photo sharing"><img src="https://farm3.static.flickr.com/2399/1507140417_c60248b8b5_m.jpg" style="border: 2px solid #000000" /></a>

<span style="font-size: 0.9em; margin-top: 0px"><a href="https://www.flickr.com/photos/26382484@N00/1507140417/">Farm buildings</a>

Originally uploaded by <a href="https://www.flickr.com/people/26382484@N00/">jokke-svin.dk</a>
</span>
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test

How can I “revert” what I’ve done, when I can’t access the admin page?

Thanks in advance!