Should I bother learning XHTML if most websites are built with FLASH nowadays?

I'm a print designer who wants to transition to web design, but I don't want to waste valuable time learning applications that will only be obsolete in a year or two. If I had to choose only one: XHTML, Dreamweaver, or FLASH - which one would be most beneficial in the future and allow me to hit the road running, since Web sites are so complicated today.