Learn Hardcore German: Auf der Webseite erklärt die Firma ihre Regeln zum Datenschutz und fragt nach einem sicheren Passwort. - On the website the company explains its rules on data protection and asks for a secure password.

auf der Webseite = on the website (location)
auf die Webseite = onto the website (movement), e.g. Er lädt die Datei auf die Webseite hoch (He uploads the file onto the website).

Because Webseite is feminine (die Webseite), the dative singular article is der, giving auf der Webseite.

Could I also say Die Firma erklärt auf der Webseite ihre Regeln …? Why does the sentence start with Auf der Webseite?

Yes, Die Firma erklärt auf der Webseite ihre Regeln … is also correct.

German main clauses follow the verb-second rule: the finite verb (here erklärt) must be the second element. The first element can be:

the subject: Die Firma erklärt …
an adverbial phrase: Auf der Webseite erklärt …
an object: Ihre Regeln erklärt die Firma … (less usual here, but possible for emphasis)

In the given sentence, Auf der Webseite is pulled to the front to emphasize where the company explains the rules. That whole phrase counts as one element, so the verb erklärt must come right after it.

Why is it die Firma? Could it be a different gender, and is there any difference to das Unternehmen?

Firma is a feminine noun in German:

die Firma (singular)
die Firmen (plural)

You cannot say das Firma; that would be grammatically wrong.

Unternehmen is a different word for company, but it is neuter:

das Unternehmen (singular)
die Unternehmen (plural)

Both die Firma and das Unternehmen can mean company, but:

Firma often refers more to the name/brand of a business or a relatively concrete company.
Unternehmen can sound a bit more formal or abstract, like enterprise or corporation.

In this sentence, die Firma just means the company.

Why is it ihre Regeln and not seine Regeln? What does ihre refer to?

The possessive pronoun must match the gender and number of the possessor, not of the thing possessed.

Possessor: die Firma (feminine, singular)
Thing possessed: Regeln (plural)

For a feminine singular possessor (die Firma), the corresponding possessive is ihr- (her/its).

Since Regeln is plural, you use the plural form ihre:

ihre Regeln = her/its rules (the company’s rules)

You would use seine Regeln only if the possessor were masculine or neuter singular, e.g.:

der Verein (masc.) → seine Regeln
das Unternehmen (neut.) → seine Regeln

Here, ihre = its (the company’s), not “their”.

What exactly does Regeln zum Datenschutz mean, and what is zum here?

Regeln zum Datenschutz literally means rules for data protection.

Regeln = rules
zu dem = to the / for the
Datenschutz = data protection / protection of data

In everyday German, zu dem is almost always contracted to zum:

zu dem Datenschutz → zum Datenschutz

The preposition zu here means roughly concerning / about / for, and it always takes the dative. Datenschutz is masculine (der Datenschutz), so dative singular is dem → zu dem → zum.

You could also say:

Regeln über den Datenschutz (rules about data protection) – slightly different nuance but similar meaning.

What does the compound noun Datenschutz literally mean?

Datenschutz is a compound of:

die Daten = data
der Schutz = protection

So literally: protection of data → data protection.

It’s a single masculine noun: der Datenschutz.

It’s very common in German in legal and IT contexts and includes ideas like privacy policy, protection of personal information, etc.

Why is there no comma before und fragt in … erklärt die Firma ihre Regeln … und fragt nach einem sicheren Passwort?

Here und connects two verbs with the same subject in one main clause:

erklärt die Firma ihre Regeln …
(die Firma) fragt nach einem sicheren Passwort

In German, when und (or oder) simply joins two verbs or predicates with the same subject in a main clause, you usually do not put a comma:

Er öffnet die Tür und geht hinaus.
Sie liest ein Buch und hört Musik.

You would have a comma if you had two separate clauses where a comma is required, or with more complex structures, but in this basic coordination you normally leave the comma out.

Why does the verb fragen use nach here? Why not fragt für or fragt ein sicheres Passwort?

In German, fragen combines with different structures depending on meaning:

jemanden nach etwas fragen
= to ask someone about / for something
- Die Firma fragt (dich) nach einem sicheren Passwort.
  (The company asks you for a secure password.)
jemanden etwas fragen
= to ask someone something (a question)
- Ich frage dich etwas.

But fragen für does not mean ask for in the sense of request.

English often uses the verb ask for both ask a question and request. German typically uses:

fragen nach + Dativ = ask about / ask for (information, something needed)
jemanden um etwas bitten = ask someone for something / request something

So if you want “ask for a secure password,” you either say:

nach einem sicheren Passwort fragen (as in the sentence), or
um ein sicheres Passwort bitten (more like “request a secure password”).

Why is it nach einem sicheren Passwort and not nach ein sicheres Passwort or nach einen sicheren Passwort?

The preposition nach always takes the dative case.

The noun Passwort is neuter:

das Passwort (nominative/accusative)
dem Passwort (dative)

With the indefinite article ein, the dative neuter form is einem:

nominative: ein sicheres Passwort
accusative: ein sicheres Passwort
dative: einem sicheren Passwort
genitive: eines sicheren Passwortes/Passworts

So after nach, you must use dative:

nach einem sicheren Passwort

nach ein sicheres Passwort (no case change) and nach einen sicheren Passwort (accusative einen and wrong gender) are both ungrammatical.

Why does the adjective appear as sicheren in einem sicheren Passwort and not as sichere or sicheres?

This is about adjective endings (Adjektivendungen) in German. The ending depends on:

the case (here: dative),
the gender (here: neuter),
the article type (here: indefinite article ein).

For neuter, dative, singular with an indefinite article, the pattern is:

article: einem
adjective: -en ending
noun: Passwort

So we get: einem sicheren Passwort.

Compare:

nominative neuter: ein sicheres Passwort
accusative neuter: ein sicheres Passwort
dative neuter: einem sicheren Passwort
genitive neuter: eines sicheren Passwortes/Passworts

You only see sicheres in the nominative/accusative neuter, not in the dative.

Could I say fragt um ein sicheres Passwort instead of fragt nach einem sicheren Passwort?

No, fragen um is not idiomatic German.

To express ask for a secure password, you have two different verbs:

fragen nach
- dative
- Die Firma fragt nach einem sicheren Passwort.
  = The company asks for a secure password.
bitten um
- accusative
- Die Firma bittet um ein sicheres Passwort.
  = The company requests a secure password.

So you can say:

nach einem sicheren Passwort fragen
um ein sicheres Passwort bitten

but not um ein sicheres Passwort fragen.

Does ein sicheres Passwort mean a secure password or a strong password? Is there a difference in German?

Literally, sicher means safe / secure.
In the context of passwords, it usually overlaps with English secure or strong:

ein sicheres Passwort = a secure / strong password

In IT/security language, you also find:

ein starkes Passwort = literally a strong password

Both are used. sicheres Passwort stresses the idea that the password is safe from being guessed or hacked, while starkes Passwort is a bit more technical/jargon-like (focus on strength, complexity). In everyday use, sicheres Passwort is very common and natural.