Does your meringue slide around on the top of your pie? This could be due to one or two things. First, an over-whipped meringue slides on the lemon filling for the same reason it weeps: the sugar is coming out of the meringue. Second, the shock of a drastic temperature change can cause sliding meringue. Putting room-temperature meringue onto an ice-cold filling and then cooking it in a hot oven can cause the meringue to sweat, and the filling might even get condensation on its surface; this moisture layer will cause the meringue to slide. To avoid this, bake the meringue on a pie filling that has fully cooled to room temperature, or, if the filling was made ahead of time and chilled, give the pie a chance to warm up a little before baking on the meringue.