what is style.css?ver=1 tag?

Question

I found out that some websites use css tag like style.css?ver=1. What is this?

What is purpose of ?ver=1?

How do I do it in code?

Answer 1

IMO a better way to do this would be to include a hash generated off of the file size or a checksum based on the file contents or last-modified date. That way you don't have to update some version number and just let the number be driven off of the file's changing properties.