1. A system for controlling and monitoring the rendering of electronic content to a viewer via an electronic communications network, comprising: a system-end computer equipped and configured for communications via said electronic communications network, including one or more computer processors and one or more system servers communicating via said electronic communications network with one or more electronic content pages, said one or more electronic content pages having one or more content rendering areas, said one or more electronic content pages being remotely accessible via said electronic communications network by a viewer, said viewer having an electronic network communications device with a browser application having a window having a viewable area defined by said window's dimensions and scrolling position for perceiving said one or more electronic content pages, said viewer's electronic network communications device further comprising a display screen for perceiving said browser window; said system further comprising an electronic database for storing one or more records identifying said one or more electronic content pages, and said one or more content rendering areas within said one or more electronic content pages, and one or more content files for rendering at said one or more content rendering areas; one or more electronic content file servers for storing said one or more electronic content files; one or more electronic network communications interface software applications providing an electronic user interface for receiving from system users communicating via said electronic communications network data designating one or more of said electronic content pages, one or more of said content rendering areas within said one or more electronic content pages and one or more of said electronic content files for rendering at said one or more content rendering areas, and for creating a record for storage in said system database containing said data, and for assigning an identification code to said data record and generating a tag for placement on said designated one or more electronic content pages, said tag having a reference to said stored data record identification code and a link to a system custom software application; said tag, when the content page wherein said tag is placed is requested by said viewer communicating via said electronic communications network via said electronic communications device and browser application, causing a communication to be sent from said electronic content page wherein said tag is placed to said system custom software application; said system custom software application executing when said communication from said tag is received to retrieve said data from said stored data record corresponding to said data record identification code referenced in said tag and generating and writing to said designated electronic content page a correlator code; said correlator code generating a code for marking said one or more content rendering areas on said one or more electronic content pages designated in said stored data record and causing said one or more electronic content files designated in said stored data record to be retrieved and loaded at said one or more designated content rendering areas designated in said stored data record; and said correlator code further determining, via retrieval of information from said browser application, whether a said content page rendering area designated in said stored data record is within said browser window dimensions and scrolling position and whether said browser window is the primary window open on said display device of said viewer's electronic communications device.