how to writte a look like javascript code to block acces to my web site while the authentification is not done? checkbox

Question

pictures checkbox before acces to the site

Answer 1

as simple as that?! woow. i'm a beginner in programming and it's just fascinate me. thank you a lot sir

Answer 2

what does this mean $(p:a)

Answer 3

if (!user){
do this
} else {
do that
}