Sample Tag: VMAP Session Ad Rule Pre-roll

https://pubads.g.doubleclick.net/gampad/ads?iu=/21775744923/external/vmap_ad_samples&sz=640x480&cust_params=sar%3Da0f2&ciu_szs=300x250&ad_rule=1&gdfp_req=1&output=vmap&unviewed_position_start=1&env=vp&impl=s&correlator=