Learn Hardcore Norwegian: Før innlogging på nettsiden skriver jeg inn brukernavn og passord. - Before logging in to the website I type in username and password.

So før innlogging (på nettsiden) literally means before (the) login (on the website), very close to English before login on the website or more naturally before logging in to the website.

You could also say:

Før jeg logger inn på nettsiden, skriver jeg inn brukernavn og passord.
= Before I log in to the website, I type in my username and password.

Both are correct. Using the noun (før innlogging) is a bit more compact and can sound slightly more formal or technical (e.g. in instructions, documentation, etc.).

Why does the verb come after jeg: skriver jeg inn instead of jeg skriver inn?

This is because of the V2 rule in Norwegian main clauses: the finite verb must be in second position in the clause.

Neutral word order:
- Jeg skriver inn brukernavn og passord.
  (Subject first → then verb: jeg = 1st, skriver = 2nd)
When you move something to the front (here: Før innlogging på nettsiden), that element takes the first position. The verb must still be second, so the subject moves after the verb:
- Før innlogging på nettsiden skriver jeg inn brukernavn og passord.
  Fronted adverbial (før innlogging på nettsiden) = 1st
  Verb (skriver) = 2nd
  Subject (jeg) = 3rd

If you started with jeg, you would say Jeg skriver inn ..., but once you move Før innlogging på nettsiden to the front, you must invert to skriver jeg.

Why is it på nettsiden and not på netttsida, på en nettside, or something with til or i?

Several things are going on:

Preposition: hvorfor “på”?
For websites, Norwegian typically uses på:
- på nettsiden = on the website
- på Facebook, på VG.no, på siden (on the page)
Til expresses movement towards something (to):
- Jeg går til nettsiden = I go to the website (I navigate to it)
I is generally “in” (inside something):
- i boka, i dokumentet, but not usually for websites.
Definite form: hvorfor “nettsiden”?
nettsiden = the website
en nettside = a website (indefinite)
In your sentence, you’re apparently talking about a specific website that both speaker and listener know about (e.g. your bank’s site), so the definite form nettsiden makes sense.
You could say:
- Før innlogging på en nettside ...
  = Before logging in on a website ... (any website, not specific)
Bokmål variant: “nettsiden” vs “nettsida”
- nettsiden = standard Bokmål definite form.
- nettsida = more colloquial / dialectal / Nynorsk‑influenced form that is also allowed in some Bokmål varieties.

In neutral written Bokmål, på nettsiden is the most standard choice here.

Can I move inn? Is skriver inn one word or two, and where can I put inn?

Skrive inn is a verb + particle combination, similar to English type in / enter.

The dictionary form is å skrive inn = to type in / enter.
In main clauses, they are usually separated:
- Jeg skriver inn brukernavn og passord.

You cannot freely move inn around; these are the typical patterns:

Normal:
- Jeg skriver inn brukernavn og passord.
With inversion (fronted adverbial):
- Før innlogging på nettsiden skriver jeg inn brukernavn og passord.
With pronoun object, the particle can sometimes move:
- Jeg skriver det inn. (common)
- Jeg skriver inn det. (also possible, but less natural with pronouns)

You cannot say:

Før innlogging på nettsiden inn skriver jeg brukernavn og passord. ✗

So: think of skrive inn as a two‑part verb, but with fairly fixed ordering: [verb] [particle] [object], except that with pronouns [verb] [pronoun] [particle] is preferred.

Why is there no article before brukernavn og passord? Could I say brukernavnet og passordet?

In Norwegian, when you talk about things in a general / non‑specific way, you often use the bare noun (no article), especially in instructional or technical language:

Jeg skriver inn brukernavn og passord.
= I type in username and password. (general, not your particular username)

This is similar to English in instructions: Enter username and password.

You can use the definite forms:

Jeg skriver inn brukernavnet og passordet.
= I type in the username and the password.

That sounds like you’re referring to a particular, already known username and password in this context. It’s grammatically correct, but for describing the general procedure (what you usually do when logging in), the bare form brukernavn og passord is more natural.

What is the difference between brukernavn and something like brukerens navn or bruker navn?

bruker = user
navn = name
brukernavn = username (compound noun)

brukernavn is the standard word for a login name / username (like john_smith92).

Comparisons:

brukernavn
- Fixed technical term, like English username.
- Used for accounts, logins, etc.
brukerens navn
- Literally: the user’s name (possessive form).
- Refers to the person’s actual real‑world name (e.g. “John Smith”), not their login identifier.
bruker navn
- Means (someone) uses a name (verb + object), not a noun phrase.
- E.g. Hun bruker navn i stedet for koder. = She uses names instead of codes.

So in this sentence, for login credentials, you must use brukernavn.

Is passord singular or plural here? How do you make the plural of passord?

In brukernavn og passord, passord is singular indefinite (just like brukernavn is singular indefinite).

Many loanwords in Norwegian have the same form for singular and plural, and passord is often used like that:

Singular:
- et passord = a password
- passord = password (indefinite)
Plural (colloquial, often same form):
- flere passord = several passwords
- to passord = two passwords

Some speakers may use passorder as a plural in informal speech, but passord (unchanged) is common and accepted as a plural form as well. In your sentence, context makes it clear you mean one password: brukernavn og (ett) passord.

Could I say Før jeg logger inn på nettsiden, skriver jeg inn brukernavn og passord instead? Is there a difference?

Yes, you can, and it’s perfectly correct:

Før innlogging på nettsiden skriver jeg inn brukernavn og passord.
Før jeg logger inn på nettsiden, skriver jeg inn brukernavn og passord.

Differences:

Structure
- Før innlogging ... uses a noun (innlogging).
- Før jeg logger inn ... uses a subordinate clause with a finite verb (logger).
Style / tone
- Før innlogging ... is a bit more formal / technical, like something you might read in instructions, manuals, or bureaucratic texts.
- Før jeg logger inn ... sounds more everyday and personal, because of the explicit subject jeg and the finite verb.

Meaning‑wise, both express the same idea: what happens before you log in.

Should there be a comma after Før innlogging på nettsiden?

Both with and without a comma are possible here, and practice varies.

Før innlogging på nettsiden skriver jeg inn brukernavn og passord.
Før innlogging på nettsiden, skriver jeg inn brukernavn og passord.

In modern Norwegian punctuation:

A fronted adverbial like Før innlogging på nettsiden does not require a comma before the main clause.
Many style guides prefer no comma in this exact case, so the first version is often recommended in contemporary Bokmål.

You must use a comma before a full subordinate clause if it comes first:

Før jeg logger inn på nettsiden, skriver jeg inn brukernavn og passord.
(Here the comma is standard.)

So for your original sentence with a noun phrase fronted, leaving out the comma is entirely correct and stylistically up‑to‑date.

Can I replace skriver inn with other verbs like taster inn or legger inn? Do they mean the same thing?

Yes, there are several verbs you might see in this context. They’re close in meaning but with slightly different nuances:

skrive inn
- Very common and neutral for entering text (typing).
- Jeg skriver inn brukernavn og passord.
  = I type in / enter my username and password.
taste inn
- Literally “key in” (from tast = key/button).
- Emphasises pressing keys or buttons, e.g. on a keyboard, keypad, or PIN pad.
- Jeg taster inn PIN-koden.
legge inn
- More general “put in / add / enter (into a system)”.
- Often used when adding data to a system, uploading, or configuring something.
- Jeg legger inn opplysningene i systemet.

For username and password on a website, skrive inn (and taste inn) are both natural, but skrive inn is probably the most common generic option in written instructions.