Disallow Rule Must Start with a Slash
If you’re specifying a path in the robots.txt file, you must start with a slash, not a * wildcard. This was always true, but was only recently added to the documentation and Search Console testing tool.
Port Numbers in URLs Don’t Create Duplicates
URLs with default port numbers, e.g. :80, are not duplicate so don’t need to worry about them. 43 is the default port for HTTP.
Trailing Slash Doesn’t Matter for Hostnames
You don’t need to worry about including a trailing slash for Hostname only URL, e.g. your home page. It doesn’t matter as they are both the same URL, with and without a trailing slash. For all other URLs, it doesn’t matter which you choose but you must be consistent.
URLs with Hashbangs Won’t be Indexed
URLs with hashbangs won’t be indexed, so if they are required to produce unique pages, you’ll need to migrate to a traditional URL structure without the hashbang.
Mixing Character Case in URLs
Mixing different case characters in URLs can cause problems.
URL Issues Create Duplicate Pages
Duplicate URLs from inconsistent ordering, case inconstistency, and session IDs can be fixed with canonical tags if the issue is minor, but it still creates crawling issues if there are many instances.
All Top Level Domains Are Equal
Google doesn’t treat any top-level domains differently. So a .com is treated no differently to a .info.
Number of Paths in a URL Doesn’t Matter
The number of paths used in a URL doesn’t matter.