Under the "advanced notes 一" section, the translation reads:

The boy read a boy while I was waiting for the girl.

Perhaps this should be "the boy read a book"?

Also, looking at the "fixed" sentence for that example, I think it's a little vague how the incorrect

私は彼女を待ちながら男の子は本を読みました。

is changed into the correct

私が彼女を待つ間、少年は本を読んだ。

In the correct sentence, aren't there still two actors, 私 and 少年? Is it acceptable because only 少年 is marked as the topic of the sentence using は? (In any case, it might also be clearer to use either 少年 or 男の子 in both sentences instead of changing it, which was probably an oversight.)

The site doesn't know how to mark parts of the sentence red/green yet, aside from the model sentences. Is something I'll have to add in later. I will fix the noun, the typo, and add a bit more explanation about correction.

Ah, somehow I managed to completely gloss over the 間 in that sentence, thanks for pointing it out キャシー! I had guessed that the が made it a subordinate clause, but somehow managed to completely miss that the particle had changed...

Thanks for clearing things up, マイケル.

I'd like to add some explanation about the difference of "間" and "間に".

1) "間" indicates the breadth of a defined amount of time that has a beginning and an end.　Therefore after "間" a word expresses a continuous action or condition comes.
Ex.
・校長先生が話している間、その生徒は（ずっと）寝ていました。
The student slept (all the time) the principal was talking.
・春休みの間、毎日友達と釣りに行きました。
I went fishing with my friend every day through the spring break.
・私が夕飯を作る間、弟はテレビを見ていました。
My brother was watching TV during I was cooking dinner.

* "ずっと（all the time, through, over the period）" is often used with "間",but never with "間に".

2) On the one hand,"間に" express "before the defined timeframe is over". Therefore an expression of momentariness comes after "間に",which express the action/event take places at sometime during the period "間" shows. 　
Ex.
・校長先生が話している間に、その生徒は逃げ出しました。
The student run away sometime during the principal was talking.
・春休みの間に、友達を訪ねたいと思います。
I am going to visit my friend at sometime during the spring break/before the spring break is over.

*In other word, you use an expression of continuation with "間", while you use “間に” with expression shows that the event/action happens and/or ends in a moment.

I think this is one of the difficult parts for English speaking students,whose language doesn't have such restriction on verbs/predicate you can use with a specific expression. I hope my explanation will help your understanding of "間" and "間に".

Oh man. So technical and specific. At the advanced notes, it says that 間 can be used the same as　ながら。Does this mean that I can replace all ながらs with 間s, but not the other way around?

Actually. When using ‾ながら the main action should be the latter. If you study Japanese grammar you notice that the message they convey appears on the last part of their sentence. For example, わたしのなまえnameです. Or 犬と散歩しています。I'm strolling with my dog. inu to...

Unless the translation has been changed in the last seven hours, that's what it says - but the highlighting is in the wrong place, so maybe that's what you meant? It really should be "[I read a book while] I was waiting for the girl." (Brackets marking highlighting).

No, the example is correct. The main act was waiting for the girl - that's what defines how long the other action lasts, or what triggered them happening at the same time, so that's the one that follows "while". English is flexible enough that you can get away with saying "I waited for the girl while reading a book," because we know what you mean, but technically that implies that the main action is reading the book.

It might not be as obvious there, because the actual meaning - that you're waiting for her while you read your book, and once you're done reading you're leaving whether she's there or not - doesn't seem right, so we automatically interpret it the other way.

Think about "I watch TV while I do my homework" versus "I do homework while I watch TV." In the first, you are in the habit of turning on the TV when you sit down to do homework, while in the second you are in the habit of picking up your homework when you sit down to watch TV, and you've probably got more attention on the TV in the second case than in the first. We feel like we can interpret it the other way if we need to because English is less strict on this, but technically that's the right way.

One reason you might be inclined to write it the other way around is that it puts more emphasis in the sentence on the waiting, which is clearly more emphasized in the Japanese; to put the emphasis on the waiting rather than the reading, you change the order of the sentence: "While I wait for the girl, I am reading a book." Semantically, this sentence is identical to the original sentence, but it emphasizes the waiting and makes the book reading less important.

The problem with translation is when you get into translating too closely, because English and Japanese don't always line up. When I read the example sentence, it actually came across my brain as "Reading a book, I wait for the girl," which of course feels stilted and formal, but probably follows the Japanese more closely.

I can definitely see where confusion came in - in the example sentences, three out of the four are in the order you suggested, with the fourth one the other way, but the usage notes match the example sentence. The trouble comes in that ながら is actually not a whole lot like "while", but it's the easiest equivalent to use. They have different rules for choosing which part goes where, which sometimes line up and sometimes don't. :P

Hello! This can also be used in the past tense, right? For example, would this be correct? 朝ご飯を[color=red]食べたながら[/color]、日本語を勉強しました。

Oh, ok. That makes sense. :) Thanks!

Yes - the English was correct, but the letter marker was not. Fixed!