Если Вы заметите лишний пробел, лучше сразу исправить его.

Capitalized Вы is a polite/formal way to address one person in writing. It can also be the normal plural you, but in this kind of sentence it usually reads as formal singular.

So:

• ты = informal singular
• вы = plural, or polite singular
• Вы = especially polite/formal written form

A less formal version would be:

Если ты заметишь лишний пробел, лучше сразу исправить его.

Заметите is from the perfective verb заметить. In Russian, perfective verbs do not have a true present tense; their non-past forms usually refer to the future.

So:

• замечать / заметить = imperfective / perfective pair
• заметите = you will notice

After если, Russian often uses this future-looking perfective form where English uses the present:

• Если заметите... = If you notice...

This is completely normal Russian grammar.

The perfective заметить focuses on a single completed event: the moment you notice the extra space.

That fits the meaning well:

• one occasion of noticing
• a concrete result: you become aware of it

If you used the imperfective idea, it would suggest a more general or repeated process of noticing, which is less natural here.

Лишний means extra, unnecessary, or superfluous.

So лишний пробел is an extra space—for example, an unwanted blank space in text.

It agrees with пробел in gender, number, and case:

• пробел = masculine singular
• лишний = masculine singular form

It is in the accusative case because it is the direct object of заметите.

You notice what? → лишний пробел

Since пробел is masculine and inanimate, its accusative form is the same as the nominative:

• nominative: лишний пробел
• accusative: лишний пробел

So the form does not change visibly here.

Лучше исправить means it’s better to correct it. This is a softer, more general recommendation than a direct command.

Compare:

• лучше сразу исправить его = it’s better to correct it right away
• сразу исправьте его = correct it right away (more direct)

Russian often uses лучше + infinitive to give advice in a polite or neutral way.

Исправить is perfective, so it emphasizes completing the correction.

That makes sense here because the action is a one-time fix:

• notice the extra space
• correct it

If you said исправлять, it would sound more like an ongoing process or habitual action, which is not the main idea in this sentence.

Сразу means right away, immediately, or at once.

It adds the idea that the correction should be done without delay:

• лучше исправить его = it’s better to correct it
• лучше сразу исправить его = it’s better to correct it immediately

This word is very common in everyday Russian.

Его means it/him, and here it refers to пробел.

Because пробел is masculine singular, the pronoun is masculine singular too:

• пробел → его

In this sentence, его is the direct object of исправить:

• исправить что? → его

So literally: correct it.

Sometimes Russian can omit an object if it is very obvious from context, but here исправить его sounds clearer and more natural.

Without его, the sentence:

Если Вы заметите лишний пробел, лучше сразу исправить.

is possible, but it can sound slightly less complete, because исправить usually makes the listener expect an object: correct what?

So keeping его is the safest and most natural choice.

Because Если Вы заметите лишний пробел is a subordinate clause introduced by если (if).

In Russian, subordinate clauses are normally separated from the main clause by a comma:

• Если Вы заметите лишний пробел, лучше сразу исправить его.

This is standard punctuation.

Yes. Russian word order is flexible, though each version may sound slightly different in emphasis.

The original sentence is very natural:

Если Вы заметите лишний пробел, лучше сразу исправить его.

Other possible orders include:

• Если Вы заметите лишний пробел, его лучше сразу исправить.
• Лишний пробел, если Вы его заметите, лучше сразу исправить.

But the original is probably the clearest and most neutral.

Because Russian and English handle if-clauses differently.

In English, we normally say:

• If you notice...

not If you will notice...

In Russian, the perfective non-past form often expresses future meaning after если:

• Если Вы заметите...

So even though заметите is future in meaning, it is exactly the normal form Russian uses here.