The proposed study presents the results of an experiment on the combined effects of impact factors included in the ‘contextual fidelity’ model of user experience developed in 2011. The four groups of factors described in this model simultaneously affect user experience and shape usability of interfaces, including creating hardly predictable combinatorial (e.g., cumulative or compensatory) effects in task performance efficiency. Our study investigates the combined impact of aesthetic properties of webpage design at the micro- and macro-level of interface design and task performance of different cognitive intensities, while also taking into account the cultural belonging of given web portals. Our sample includes four Russian-language versions of large-scale Russian and Chinese media portals with varying design quality at two different levels of page layout (micro- and macro-), on which task performance is tested in two conditions, namely with and without a time limit. Thus, we co-measured the combined impact of four parameters: design quality on two levels, cultural belonging, and type of task based on time constraint – upon the user performance efficiency. We evaluated the resulting user psychophysiological states that form under the combined impact of ‘contextual fidelity’ factors via assessing cognitive productivity and psycho-emotional strain (stress and fatigue), which were used as dependent variables. As the results of the experiment showed, differences at the macro-level of design have a stronger effect on the efficiency of cognitive processes; at the same time, the emotional states of users show relative stability. In the case of micro-level differences, the impact on users’ psycho-emotional states appears to be more significant than on cognitive processes. Small cultural differences in the formation of effects are also noted.