I created a visualforce page for the opportunity object. I turned it into a force.com. My issue is when I open the visualforce add updates to any field and click the save button the record information doesnt change. I have the code below. If anyone could help me find a solution, i would appreciate it. 
 

<apex:page standardcontroller="Opportunity" showheader="false"   >



<style type="text/CSS">


body{
color:ffffff;
}

h2{
   font-size:14px; 
   font-family:Arial, Sans-Serif, Garamond;  
   border-bottom-width: 0px;
   border-bottom-style: solid;
   padding:13px,0px,13px,0px;
   
   color:#fff;
   
   
}

th{
   padding-top: 13px;
   margin-bottom: 25px;
}
   
td{
   padding-bottom: 10px;
}
div{
background-color:#000000;
font-color:#ffffff;
height:20px;
}

.title{
   font-size:20px; 
   font-family:Arial, Sans-Serif, Garamond;  
}
</style>


<apex:form >

           
<table align="center" style="text-align:center" width="400px" styleClass="hd">
    <tr ><td class="title">Request for Special Payment </td></tr><tr><td><apex:commandButton immediate="true" action="{!save}"  value="Save"/></td></tr></table>
   
        <table>
         <tr>
           <div> <h2>Opportunity Information</h2></div>
        </tr>
            <tr>
                <th>Date:</th> <th>Opportunity Name:</th>
            </tr>
            <tr>                 
                <td><apex:outputText value="{!Opportunity.LastModifiedDate}"/></td><td><apex:outputText value="{!Opportunity.Name} "/></td>
            </tr>



    </table>

    <table>
         <tr>
           <div> <h2>Terms Adjustment Information</h2></div>
        </tr>
            <tr>
                <th>Opportunity Account Address:</th>
            </tr>
            <tr>                 
                <td><apex:outputText value="{!Opportunity.Account.BillingStreet}"/><br /><apex:outputText value="{!Opportunity.Account.BillingCity}"/>,&nbsp;<apex:outputText value="{!Opportunity.Account.BillingState}"/>&nbsp;&nbsp;<apex:outputText value="{!Opportunity.Account.BillingPostalCode}"/></td>
            </tr>
            
            
            <tr>
                <th>Robot Model or Product Name:</th>
            </tr>
            <tr>                 
                <td><apex:outputText value="{!Opportunity.Robot_Model_or_Product_Name__c}"/></td>
            </tr>
            <tr>
                <th>Quoted Total Price:</th>
            </tr>
            <tr>                 
                <td><apex:outputText value="{!Opportunity.Total_Quoted_Amount__c}"/></td>
            </tr>
            <tr>
                <th>Required Payment Term:</th>
            </tr>
            <tr>                 
                <td><apex:outputText value="{!Opportunity.Required_Payment_Terms__c}"/></td>
            </tr>
            <tr>
                <th>Detailed Reason:</th>
            </tr>
            <tr>                 
                <td><apex:outputText value="{!Opportunity.Detailed_Reason__c}"/></td>
            </tr>



    </table>

    <table>
         <tr>
           <div> <h2>Special Instructions</h2></div>
        </tr>
            <tr>
                <th>Special Instructions</th></tr>
            <tr>                 
                <td><apex:outputText value="{!Opportunity.Special_Instructions__c}"/></td>
            </tr>



    </table>

    <table>
         <tr>
           <div> <h2>Requestor Information:</h2></div>
        </tr>
            <tr>
                <th>Requestor:</th> &nbsp;<th>Submitted Date: </th>
            </tr>
            <tr>                 
                <td><apex:outputText value="{!Opportunity.Request_Submitted_By__c}"/></td>&nbsp;&nbsp;<td><apex:outputText value="{!Opportunity.Date_Submitted__c}"/></td>
            </tr>

</table>

<table>
         <tr>
           <div> <h2>DNB Results</h2></div>
        </tr>
            <tr>
                <th>DNB Results:</th>
            </tr>
            <tr>                 
                <td><apex:inputText value="{!Opportunity.DNB_Results__c}" style="width: 300px; height: 30px" /></td>
            </tr>
            <tr>
                <th>Controller Approve Request:</th> 
            </tr>
            <tr>                 
                <td><apex:inputCheckbox value="{!Opportunity.Request_Submitted_By__c}"/></td>
            </tr>

           
            <tr>
                <th>Controller’s Comments:</th>
            </tr>
            <tr>                 
                <td><apex:inputTextarea value="{!Opportunity.Controller_s_Comments__c}" style="width: 400px; height: 150px" /></td>
            </tr>
 </table>
    
 </apex:form>
</apex:page>