Not pronouncing the "h" in "herb". Or the "l" in "solder".
Also, two spaces after a full stop. I thought we stopped doing that in the '90s. And the Internet had killed it off, because HTML just won't display more than one space. But more recently, some platforms have started actually showing multiple spaces again. It just looks so damn wrong.
Oh, and one that occurred to me as a result of writing that previous paragraph. When people write "90's" to refer to the decade of the '90s. Misuse of apostrophes in general, but particularly when it's after a number, acronym, or letter. Mind your Ps and Qs, not P's and Q's.