If you develop with ASP.NET Core 2.0 or later and you are using TempData, you may run into a 400 error saying your request headers is too long. I've recently encountered this while writing a blog post, it happens when I try to preview the post.
If you ever get these CS0246 compiler error saying "type or namespace name could not be found" and pointing to your ".g.cshtml.cs" files of your Asp.net Core application, go check your ".cshtml" files.
An unit test failed when I built my code on BitBucket, it threw System.TimeZoneNotFoundException. It happens where I try to convert a UTC Time to local time in a specific time zone. Interestingly the same unit test passes on my local running Windows 10 and on Appveyor.
I’ve been testing my live site extensively this past month, posting, reposting and then I found my site’s Google search results come up with broken links. If you ever need to update your site with new URLs on existing resources, you want to think about the SEO implications first.