We study style-aware prompt-to-webpage generation: producing executable webpages that preserve content, functionality, and abstract aesthetic intent. We identify the design-intent bottleneck and introduce three components to address it: Web4Style, a brief-based diagnostic benchmark; WebWeaver, a shared-state framework that constructs and propagates an explicit style contract; and WebJudge, a structured multimodal evaluator for content, function, and visual aesthetics. Experiments across three backbone models show that WebWeaver improves over direct generation and representative web/code-generation agents in both automatic and human evaluation. These results highlight style contracts as a missing intermediate layer for reliable prompt-to-webpage generation.