I was putting together my tides dashboards -here- and found a source of tidal data on a web page.
Lucky day, thought I: with Tableau's copy-and-paste data-grabbing ability it promised to be a simple matter of highlighting the table, ctrl-c, switch the Tableau, ctrl-v, and away we go.
Sadly, my hopes were dashed. Upon pasting the data into Tableau it wasn't at all the same as the web page presented it. In fact, it was pretty much unusable. I was a wee bit miffed, my plans to get back to the beach, nice new tides tables showing up on my iPad were dashed.
The trouble turned out to be the way Tableau recognizes data copied from HTML tables. In this specific instance, the presence of a <br> tag in one of the table headers to make it easier to read was interpreted by Tableau as an end-of-line signal, which scrambled the record processing in the middle of reading the field name first record.
The workbook below, published to Tableau Public, details the situation.
Interestingly, when I contacted Tableau about this situation they told me that it's behaving precisely as intended, that <br> tags are explicitly interpreted as end of record characters because "those are the rules".