Is it considered "safe" to use URL constructed from random characters like this?

http://example.com/EU3uc654/Photos

I'd like to put some files/picture galleries on a webserver that are only to be accessed by a small group of users. My main concern is that the files should not get picked up by search-engines or curious power-users that poke around my site.

I've set up an .htaccess file, just to notice that clicking on http://user:pass@url/ links doesn't work well with some browsers/email clients, prompting dialogs and warnings messages that confuse my not-too-computer-savy users.