The Canada Revenue Agency's website, which includes the Charities Directorate, will apparently be moving to the new www.canada.ca domain on July 11, 2017.  The old CRA pages will remain up during the interim period of the move.   Hopefully those visitors who go to pages on the old website will be automatically redirected to the new website.

I have written about this change and my concerns in a blog entitled “Government of Canada to combine all Federal government websites into Canada.ca“.  

The CRA page will be https://www.canada.ca/en/services/taxes.html

The Charities Directorate page will be https://www.canada.ca/en/services/taxes/charities.html

Ultimately if the www.cra-arc.gc.ca/charitiesandgiving link/website is not available presumably CRA will provide its suggestions as to which link should be used for receipting purposes.  As you know the regulations to the ITA state that every official donation receipt must have “the name and Internet website of the Canada Revenue Agency.”