This website creates a Cookie called RAYNET-ID to store a pseudo-random string used to identify a member as they visit various pages of the website, to confirm that they are valid members of the Eastbourne and Wealden RAYNET group and therefore allow them to see certain members only information.
Cookies are small text files created on your computer by websites you visit, to store information (like user ID's). Then can remain after you leave the website that created them, or even after you have shut down your computer.
Cookies are nor harmful, as such. One use is to track your website usage. An advert on Website A may place a Cookie on your computer, then Website B / C / D may look to see if you have that Cookie installed, thus tracking which other websites you may have visited.
You can configure your browser to either not accept Cookies from specific or all websites completely (this may prevent you from accessing some websites), or to simply 'forget' some or all Cookies when you close the browser.
For instructions on how to do this, Mr. Google is your friend.