Do Online Airfare Tickets Go Up The More That You Search Them

I Have been searching for a multi-city airfare Through All The Major discount airfare sites.And Each Time That The Same dates I search the Price change.One Day It Will Be $ 707, $ 701 The Next, A Few Days Later icts $ 658 a pair Hours Later icts $ 713 .... I dont get it it.Is The Time of Day That I keep gold searching the rental price & Demand Causing to go up?