This site can't be reached error
Here is what I did: I went to the project tab -> properties -> Web then clicked the create virtual directory and everything started working back normal.
Try this and it should work:
1-Go to your project folder and open .vs folder (keep your check hidden item-box checked as this folder may be hidden sometimes)
2- in .vs folder - open config
3- see that applicationhost config file there? Delete that thing.(Do not worry it will regenerate automatically once you recompile the project.)
In my case, it was not the application but what I was submitting. My form contained a file I was uploading and when I hit submit I would get that error. Turns out the file couldn't be uploaded because the file was in use. I just closed the file I was trying to attach and it worked.