By appending '?ver=1' to the end of a URL in an HTTP request, it appears as though the request is a GET query with parameters. However, browsers and proxies that follow best practices will not cache parameterized queries. Additionally, these well-behaved browsers and proxies should also adhere to response headers like 'Cache-control: no-cache', 'Expires', 'Last-Modified', and 'ETag', which are all designed to dictate proper caching behavior.
The usage of '?ver=1' as a method is considered inefficient because it serves as a costly workaround for site developers who may be unaware or too lazy to implement the correct response headers. Essentially, this approach results in the CSS file being requested on every page load, even though CSS files rarely, if ever, change in practice.
In light of this, my advice is simple: Avoid using this method altogether.