What is Visualforce page problem in Salesforce?

Hi,

You can take help from this example :-

<apex:page controller="Abc">
    <apex:form id="form">
        <apex:actionFunction name="loadPageContent" action="{!THREESeconds}" status="loading" reRender="form" />
    </apex:form>
    <apex:actionStatus id="loading">
        <apex:facet name="start">
            <img src="/img/loading32.gif" style="vertical-align: middle; padding-right: 1em" />
            Loading...
        </apex:facet>
    </apex:actionStatus>
    <script>
        loadPageContent();
    </script>
</apex:page>

public class Abc {
    public void THREESeconds() {
        Long startTime = DateTime.now().getTime();
        while(DateTime.now().getTime()-startTime<3000);
    }
}