Why are romantic relationships taboo? Explain based on winstons lifeI'm not exactly sure what taboo is so it's hard for me personally to understand.

Romantic relationship as part of "ownlife."  The state
allows sex/romance for procreation and procreation only ... it's almost your duty to the
state.  Despite their attempt to "legislate" romance/sex out of their lives, they are
unsuccessful.  Winston is allowed to have a "quickie" with a prostitute, largely because
there is no connection to it.  On the other hand, his relationship with Julia is a
threat because it is actually more important to him that his life; he knows this is
thoughtcrime and that it will lead to his demise, yet he goes ahead and does it anyway. 
On the other hand, Julia is interested in sex in and for itself; Winston sees some
rebellion against the state in their relationship, but she is not interested in any of
those ideas.  While he is "absorbing" the Goldstein "document," she sleeps.  Only the
proles can have romantic relationships because they are totally harmless; despite
Winston's dream that there is hope in the proles, we know that there is none, so they
are free to do whatever they want.

Hope this
helps.