Jennifer - you don't use html/css. What you do is get the citation from Find a Grave and format it like this one --
<ref>Find a Grave, database and images (accessed 02 January 2021), memorial page for William Charles Lesslie (1847–1915), {{FindAGrave|170621226}}, citing Rookwood General Cemetery, Rookwood, Cumberland Council, New South Wales, Australia ; Maintained by Grave Finder (contributor 47440664) .</ref>