dlrowehtanool is loonatheworld spelled backwards.
In preparation for Yves' debut, the official loonatheworld twitter account began posting teasers for the debut of Yves, the first member of yyxy. But instead of the normal teaser, fans noticed that the link http://www.loonatheworld.com/ on the teasers was replaced with http://dlrowehtanool.com/.
The official LOONA twitter account continued to release teasers with the website spelled backwards for all the members of yyxy, with four teasers having the http://dlrowehtanool.com/ shown and four teasers with the regular http://www.loonatheworld.com/ for each member. Fans also noticed that the teasers with the loonatheworld link were more innocent, while the teasers with dlrowehtanool were much more mature and were also featured in the teasers where there was more than one member present.
In the case of Yves, the teasers that link to loonatheworld look similar to teasers from other LOONA members, with one of the teasers depicting her in the yyxy uniform. When we look at the dlrowehtanool teasers, we see that in every one of those pictures she is dressed as her representative animal, the swan.
With Chuu, we see that in her loonatheworld teasers she is smiling and fits her cute concept. But in the dlrowehtanool teasers, she's either with Yves, or looks very serious and has darker lighting than in her "regular" teasers.
The interesting thing about Go Won is that she has three loonatheworld teasers and six dlrowehtanool teasers for her solo; four by herself and two with Chuu. In the case of her teasers, the most obvious difference between the two is her hair color, since in the teasers she has her natural black hair except in her yyxy teasers and in the dlrowehtanool teasers where she's blonde.
Olivia Hye is probably the most different from her other members, since her only dlrowehtanool teasers are with Go Won.
For beauty&thebeat, every individual teasers has the loonatheworld link, whereas the group teasers has the dlrowehtanool link.