I may be interpreting too much here, but of your 3 examples, only one looks to me like it's findable by a simple search ...
W3C allows HTML5 - yep, that's a fast search... and given the nature of your work, I'd propose stapling W3C to the top of any resource list, putting it out the team in email and a variety of other mass assimilation actions - if you're a web developer, W3C is probably one of your top ranked sites. :)
Do we have this CSS class in our stylesheets - I don't know how you're going to find that in Google? It's surely easily searchable in your codebase -- but if your stylesheets are searchable on the internet, you're either working on open source or something pretty wild.
Do you know what version of IE is most popular - only answerable on the Internet if you're talking about the wide population of "all internet users" or "internet users that hit hugely mainstream sites" - a question of statistics like this has a lot to do with whether the data supports the target user base you are trying to anticipate. Slant it even a little and you may find a different answer that what "everyone" does.
I point these out, because sometimes it's helpful to consider whether they have other reasons of asking beyond and inability to use Google. If you have an office where the response is "Google? never heard of it!" and you do web development... run, run away fast.
Other reasons for asking are:
they want to know that YOU can think deeply about the problem and come up with more than just a 5-minutes-of-research answer.
they have a situation where it really IS easier to ask the junior guy - with 12 years of experience myself, I'm so often called into architecture and business meetings that I'm more likely have Outlook and Visio open than any CM tool or SDE - so if you have it open and you have fast access to search our CSS repository, I'm going to ask you to take 5 minutes, when it'll take me 30 to get mine up and started.
this actually takes some thought and judgement - there may be a correct answer on the Internet, but there may also be 15 "correct" answers, and it'll take some digging to figure out the right one for your team. They aren't asking for you to a 5 minute task, they want someone intelligent to actually vet the answer. Google isn't absolute truth, it's a big data index. If the data is bad, the answer is wrong.
I don't know it, but I bet you do... - if I think someone knows it literally off the top of their head and can answer me without skipping a beat, I'll ask. Yep, I could Google it, but Googling takes 10 minutes, asking you on the way by takes 3... I'm asking you.
If you really ARE hitting an epidemic of Answers Best Found on Google - then you may be hitting a senior engineer who is drastically out of touch. If it's a single individual, ask your own manager what's going on here? Why is a senior guy asking you for simple answers? It's interrupting your progress and for no apparent reason.
But if you're getting this from several people, I recommend looking at the trends and seeing why it keeps coming up. Ask about it, but ask the wholistic question - you see a case where you're asked a lot of simple questions that are easily found on typical web development sites - is there a reason why others aren't finding sucess?