Access requires registration as per instructions below:
On this site, you can search manuscripts in Turkey, see some of them online, and even order digital copies of pages, paying a certain amount per page with the credit you purchase with your credit card online. I believe the search function is open to all -- you do not have to be a member to the site. You just have to make sure that you can use Turkish letters in your browsing software so that you can enter the right diacritics for modern Turkish (circumflexes do not seem to matter). After you enter a search term, like the author "Mustafa Ali," you get to a page where all the relevant manuscripts are shown to you by name, call number, etc. On that page, on the right hand side there is a column called "G." If you see an eye on that column, you can actually view the manuscript online (click on the call number, then scroll down on the next page and select a page from the thumbview) -- but only if you get a membership. After you get a membership, the page you see will have the logo of the Turkish Ministry of Culture in the center. But if you purchase some credit and "buy" a digital copy of the page, the copy you download comes without the watermark logo.
As for membership, it is pretty straight forward for Turkish citizens (just fill out the relevant information and wait for your approval -- if you do not get approved soon, e-mail them and ask what is going on, they usually respond within a business day or two), more complicated and time consuming for the rest of the world:
go to http://www.yazmakutup.gov.tr -- select "Istanbul Millet" -- click on "Yararlanma" in the menu on top -- scroll down and click on "TIKLAYINIZ" where it says "Basvuru formu icin tiklayiniz." Fill out the form and mail it to the address provided under "Iletisim" on https://www.yazmalar.gov.tr It might be a good idea to send a digital copy to Ayda Percin ( email@example.com ) who provided this information to me when I wrote to her that I would like to announce this website to my colleagues but needed to know how they could make use of this website. Good luck!