Prodigy launched online ads from the 1980s. AOL as well.

HotWired (Wired's first online venture) sold their first banner ads in 1994.

DoubleClick was founded in 1995.

Neither were limited to 90's hardware:

Web browsers were available for machines like the Amiga, launched in 1985, and today you can find people who have made simple browsers run on 8-bit home computers like the C64.