Learn Hardcore Croatian: Na mreži često čitam članak o hrvatskom jeziku. - On the internet I often read an article about the Croatian language.

Na mreži često čitam… – puts a little emphasis on where you read (online).
Često na mreži čitam… – slightly emphasizes how often.
Često čitam članak na mreži o hrvatskom jeziku. – more neutral, similar to English word order.

All of these are grammatical; the differences are mostly about what you want to highlight (place, frequency, etc.), not about correctness.

What exactly does na mreži mean? Is it the same as “on the internet”?

Literally, na mreži means “on the network”. In everyday usage it usually means “online / on the internet”.

In practice:

na mreži ≈ “online”
You will also very often hear na internetu, which is a bit more transparent to learners and very common.

So you could also say: Na internetu često čitam članak o hrvatskom jeziku.
All three: na mreži, na internetu, and the English loan online (sometimes written online, sometimes onlajn) are understandable.

Why is it na mreži (with na) and not u mreži?

With places, media, and platforms, Croatian usually uses na:

na internetu – on the internet
na televiziji – on TV
na radiju – on the radio
na mreži – on the (computer) network / online

u mreži would literally mean “in the net / inside the network” and sounds physical, like being caught in a fishing net or physically located inside some network structure. For the meaning “online”, na mreži is the normal choice.

Why is čitam used here and not pročitam?

Croatian distinguishes imperfective and perfective verbs:

čitati (čitam) – imperfective: focuses on the process or habit (I read / I am reading / I often read).
pročitati (pročitam) – perfective: focuses on a completed action (I read through / I will finish reading).

The sentence describes a habitual action (“I often read…”), so the imperfective čitam is correct.

If you said:

Na mreži sam pročitao članak… – “I (have) read / finished reading an article online…” (a completed event).

Can često go somewhere else in the sentence?

Yes. All of these are grammatical, with small nuances:

Na mreži često čitam članak o hrvatskom jeziku. (original)
Često na mreži čitam članak o hrvatskom jeziku.
Čitam često članak o hrvatskom jeziku na mreži.
Često čitam članak o hrvatskom jeziku na mreži.

Često is an adverb and can move around quite freely. Usually it goes before the verb (često čitam), but other positions are also used, often for rhythm or emphasis.

Why is it članak and not članka?

Članak is a masculine inanimate noun. In Croatian:

Nominative singular (dictionary form): članak
Accusative singular (direct object, for inanimate masculine nouns): članak (same as nominative)

So in čitam članak, the direct object is in the accusative, but it looks the same as the nominative.

Članka is:

Genitive singular: članka – “of an article” (e.g. naslov članka – the title of the article), or
Accusative singular of animate masculine nouns (not the case here).

So čitam članak is the correct form for “I read an article”.

How would I say “I often read articles” in the plural?

Plural of članak:

Nominative plural: članci – “articles”
Accusative plural: članke – (direct object)

So you would say:

Na mreži često čitam članke o hrvatskom jeziku.
= “I often read articles about the Croatian language online.”

This sounds more natural in Croatian too, because “often” usually implies more than one article over time.

What case is o hrvatskom jeziku, and why is it used after o?

O hrvatskom jeziku is in the locative case.

The preposition o (“about”) in modern standard Croatian always takes the locative:

o meni – about me
o gradu – about the city
o knjizi – about the book
o hrvatskom jeziku – about the Croatian language

So both the adjective (hrvatski) and the noun (jezik) must appear in the locative: hrvatskom jeziku.

Why do both hrvatskom and jeziku change? Why not just o hrvatski jezik?

In Croatian, adjectives must agree with the nouns they describe in:

gender,
number, and
case.

Base form (nominative): hrvatski jezik – “(the) Croatian language”
After o (which requires locative), both must switch to the locative singular masculine:

hrvatski → hrvatskom
jezik → jeziku

So:

o hrvatskom jeziku – correct
o hrvatski jezik – wrong (nominative, not locative)

Could I say o hrvatski jezik or o hrvatskog jezika?

No, not in standard modern Croatian.

o hrvatski jezik – wrong case (nominative).
o hrvatskog jezika – wrong case (genitive).

For “about Croatian (language)” you need locative:

o hrvatskom jeziku – standard, fully explicit.
In casual speech, sometimes just o hrvatskom if the context is clear, but o hrvatskom jeziku is the safest and clearest form.

Why isn’t there any word for “a” or “the” in the Croatian sentence?

Croatian has no articles (“a/an”, “the”).

Definiteness and indefiniteness are understood from:

context,
word order,
sometimes from additional words (like taj / onaj – “that”).

So čitam članak can mean:

“I read an article”
or “I read the article”
depending on what has been mentioned before and what makes sense in context.

Can I replace na mreži with na internetu or online? Are they all natural?

Yes:

Na internetu često čitam članak o hrvatskom jeziku. – very common, maybe the most typical.
Na mreži često čitam članak o hrvatskom jeziku. – also correct; a bit more “network”/technical-sounding.
Online često čitam članak o hrvatskom jeziku. – understandable, uses an English loan; informal.

All three are fine; if you want the most neutral, everyday version, use na internetu.

How do you pronounce č and ž in this sentence?

In this sentence:

č (in čitam, često, članak) is like English ch in “church”.
ž (in mreži) is like the s in “measure” or “vision”.

So:

čitam ≈ “CHEE-tahm”
često ≈ “CHES-toh”
članak ≈ “CHLAH-nahk”
mreži ≈ “MREH-zhee” (with that “zh” sound at the end).