Citing a link that was removed? I run a small blog about both the academic and professional aspects of my industry as I both teach a course at the university I am attending as well as work in the industry full time. The blog answers viewer questions and has even made some changes to core industry values which has boosted productivity and efficiency in some schools, and jobs. 

One of my posts answered a question that required extensive research and would be unbelievable without my sources. This post is almost a year old and the link that was most important to my reasoning and proof of concept is not longer active.

I am faced with two choices:


Remove the post all together because most of the credibility was in that link.
Leave the post up without the proper accreditation to my research. 


This is one of my most popular posts that effects both the academic and professional aspects of my industry and I have no way of contacting the original owner of the website that was removed.
If the page was up for a while, you can probably obtain a copy via the Internet Archive.  Once you've got that cached version, you can host it yourself, with appropriate attribution (i.e., the fact that the original source is missing, its original location and authorship, time that the snapshot was taken by the Internet Archive, etc.)

This could be a problem from a copyright perspective, but if the original material truly is abandoned, then you've got nothing to worry about.  If the owner does contact you, then either they'll likely be willing to post a copy (or its equivalent) again, obviating your need to host your own copy.  Only in the rather unlikely case they both want the material taken down and are unwilling to repost it themselves will you lose the source.