Optimizely, the creator of a website-optimization platform, has raised $28 million in Series A funding led by Benchmark Capital. Bain Capital, Battery Ventures, Google Ventures and InterWest Partners also participated in the round. Optimizely enables website owners to track engagements, clicks, conversions and other site activities to gauge Web optimization. The Y Combinator-hatched startup will use the fresh cash for international expansion, sales and marketing, and to grow its employee base and facilities. Optimizely is headquartered in San Francisco.