Hide user dropdown list in Visualforce page, please check image below

STEP1: please add a styleClass to <apex:inputFiled > as follows

    	<!-- your code goes here -- >
        <apex:inputField styleClass="hideDropdown" value="{!Account.OwnerId}"/>       

Simply add styleClass="hideDropdown" to your inputField (lookup type)

STEP2: Add custom css in your Visualforce page for hideDropdown class as follows




**NOTE:** I compressed Image else both will be in straight line

That's it!!! we're good to go.

Please comment if you feel its helpful