Sometimes after you type or paste a URL or email address into a Web link or Email field in the Add/Edit Event or other form, you see an error message that looks similar to this:
If the URL or email address looks perfectly valid and you still see the error message, the problem is almost always an extra space at the end.
Click your cursor to the far right of the Web link or email field, and then press Backspace to eliminate any stray space character. Click outside the field. The error disappears.