Standard Page Layout Like Stylesheet For Inline Visualforce Page

Add below css into your visualforce page.
Sample Code:

<style type="text/css">
.bPageBlock {
	background-color: white !important;
	border-bottom: 0px !important;
	border-left: 0px !important;
	border-right: 0px !important;
	border-radius: 0px !important;
	border-top: 0px !important;
}
</style>