HII All,
         Next visit should be greater than 30 days than Appointment Created Date:
       Next_visit__c<(Date value(Created Date )+30)
But its Showing An Error i.e, Error: Syntax error. Found 'Date'
 

I am assuming that what I trying to do is pretty basic, I am just fairly new to visual force

I would like an alert to show if a certain condition is met. In this alert I would like to have input fields that can be saved to the record. 

I created this visual force page, but it is not an alert. 
How can I make it into an alert?

<apex:page standardController="Comment__c" rendered="{!if(Comment__c.Care_Management_Related2__c==true,true,false)}">
<apex:form >
        <apex:pageBlock title="Enter Care Management Call Details">
            <apex:pageBlockSection title="Next Suggested Call" columns="1">
                <apex:inputField value="{!Comment__c.Next_Suggested_Call_Date__c}"
                label="next suggested call date"/>
                <apex:inputText value="{!Comment__c.Next_Suggested_Call_Description__c}"
                    label="Next Suggested Call Description"/>
            </apex:pageBlockSection>
            <apex:pageBlockButtons >
                <apex:commandButton action="{!save}" value="Save"/>
            </apex:pageBlockButtons>
        </apex:pageBlock>
    </apex:form>
</apex:page>