it seems to be that they are talking about methods which are used frequently.
At the top of the page it seems that way, when they mention U-Th-Pb and Rb-Sr and K-Ar dating as chief dating methods in use today. Rb-Sr is an isochron method, and U-Th-Pb is almost always a concordia-discordia method which compensates for and detects some possible problems in a different manner.
Of course, they're way behind the times; Rb-Sr is makes up about 5% of the dating studies done today, whereas Argon-Argon (another isochron method) makes up about 25-30% of the dating studies done today (and has been important for years). U-Pb-Th makes up about 40-45% of the dating studies done today. K-Ar makes up around 10% of the dating studies done today, but is essentially never used without confirmatuon by another method becasue of its possible problems.
Unfortunately, about half the discussion that follows is just plain garbage, and the other half applies only to K-Ar dating. The discussion is just plain irrelevant to 90% or so of the dating methods in use today! It does not apply to Rb-Sr, Ar-Ar, Sm-Nd, or U-Th-Pb dating!
Iso is not used frequently.
Incorect. Argon-Argon dating is an isochron method and makes up approximately 25-30% of the studies performed today. Rb-Sr and Sm-Nd are both isochron methods and each makes up about 5% of the studies that are performed today, so isochron methods make up about 35-40% of the studies that are performed today, and the percentage was higher in the 1980's and 1990's.
However, U-Th-Pb concordia-discordia is where it's at, and where it's been at for many years, and that's a kettle of fish that's not even addressed by the site that you posted.