First, notice that the link in the top right appends a number to the current url, and that this number changes for each ad (minus the first and second ads, which share #7). Indexing into each ad by each respective number gets you the string NOBLE. Clicking on each letter indexed to (i.e. the letters N, O, B, L, and E in each respective ad) opens five links, whose first letters spell out GASES. Putting these together gets the final answer.
Author's notes: Originally, the idea was to solve via noticing the links, without any indexing or anything (and normally, the ads linked to the actual sites - these were actual ads in various w3schools pages). Of course teams will simply notice that clicking on a specific place doesn't lead them to the fabulous Fashion Town website and also happen to remember exactly where they clicked! Needless to say, there was some testsolving pain, and a few of them were sacrificed to make indexing into the ads a thing. Hope you enjoyed the doable version :)
All in all, I think those five ads got more than they bargained for in terms of exposure; at least for me, I've stared at that first ad more than enough to make up for all the people who scroll past, simply looking for a spare CSS tip...
(Also, thanks for falling for the rickroll yall :) It was hilarious watching the Rick Astley answers come in. It wasn't until after the hunt had started that someone suggested tracking how many people clicked it, but oh well.)