Lately, I’ve been working at improving the readings of Japanese sentences (furigana), with the very helpful collaboration of tommy_san. Each reading is now placed independently on the top of each character, instead of being systematically grouped over each word, and a new syntax allows to distribute each part of the reading over each character. This image will explain better what I mean: https://i.imgur.com/1qGof66.png (you need to look closely at the furigana to catch the differences).
Actually, this feature has been around for some time but not announced. It may seem like a very picky change, but having furigana properly aligned is very helpful for learners of the Japanese language. It’s also the only proper way of displaying furigana, as it can be observed in any Japanese book, newspaper, placard… which hopefully makes Tatoeba looking a little bit more serious among Japanese people.
Thanks for the hard work, gillux! Let me make some additional remarks.
First, you need to check "Always show transcriptions and alternative scripts" on the settings page to see machine-generated furigana. Note that these transcriptions with a warning sign are not always correct. Transcriptions without a warning sign have been added by human contributors and are much more likely to be correct. These manual transcriptions are also found on the downloads page. I plan to provide furigana for all the sentences I've written and proofread.
As gillux says, almost all furigana are now associated individually with each kanji, but some of the kanji compounds called 熟字訓 are exceptions. For example, there's a word 明日 (ashita, あした) at the beginning of gillux's example above. It's not that 明 reads "ashi" and 日 reads "ta", or 明 "a" and 日 "shita", so the three hiragana are placed evenly above two kanji. On the other hand, when one or more of the kanji are read the normal way, the furigana is divided as in normal compounds. For example, the reading of the word 時計 (tokei, とけい) is special because 時 doesn't have the reading "to". However, since 計 does normally read "kei", the furigana と is placed on top of 時 and けい on top of 計.
I think this new system will be most useful when you're looking for sentences where a specific kanji is read in a specific way. If you're interested in doing this kind of search on the website, reply to this message to let developers know.