I have had this problem before even while copying tables for other sources, not just the Internet, into InDesign text..
Basically, I need to copy several tables from a website, but in a couple of cases the tables are hundreds of rows long. The tabbing still works relatively well, except for the last column.
It does not conform to any tabs I try to set up. If a try to add another row it compresses the last two columns together and mis-aligns both columns. It is kind of hard to explain exactly what happens.
Are there any methods to copy Internet tables into InDesign documents?
Try copying to Word instead and then placing that in InDesign.