Update:

Installed hotfix 7.0.3 today, which fixed the issue. Images, .js and .css files, etc. can now be included in our templates again without having to put them in App_Themes.

However, in the instructions PDF that comes with the hotfix it says the following:

"URL Rewriting & SEO - URLs of physical files that weren't excluded from the URL rewriting engine returned a page not found error instead of regular content."

This is correct for everything but ASPX pages. If I add a page named "test.html" to the root of my project, I can go to "http://localhost:[port]/test.html" the contents are displayed correctly.

However, if I rename this file "test.aspx", it immediately gives me a 404 error. I understand that Page Templates are .aspx files, and that the "Exclude URL" can be used to make this work.
Now, in the hypothetical situation where I would copy 20 folders filled with static ASPX pages into my Kentico site (pages that are not templates), I would have to exclude all of these.

Also, in previous implentations, sometimes we would point the Page Not Found / 404 URL to something like "/error404.aspx", which would then be availabe under "http://[domain]/error404.aspx" and would show correctly if a page could not be found. This page would be a non-template page, a static ASPX file.

Now, this 404 page has to be a page based on a template. Simply pointing to the error404.aspx will give another 404. If we add an error page in the CMS and set the URL to point to that page, it works correctly.

So, I know there's a work around, but technically, the issue for physical non-template ASPX pages remains.

Hello Martin,
Thank you for reply.

Indeed, the issue was cured by the hotfix of May 10th, now our Kentico version is 7.0.4877.

Best regards,
Vasiliy