Error on VF page after preview:

The name can only contain underscores and alphanumeric characters. It must begin with a letter and be unique, and must not include spaces, end with an underscore, or contain two consecutive underscores.

I think it has to do with edit/delete command action link which I added.So kindly review and let me know where to make changes.

**controller**

public with sharing class DisplayAccWithContact3 {

    public PageReference DeleteContact() {
        return null;
    }

    public Contact con{get;set;}
    public DisplayAccWithContact3() {
        con=new contact();
    }
    public List<Contact> contacts {get; set;}
    public string SelectedContactId { get; set; }
    
    public PageReference showContacts() {
        contacts = [SELECT Name, Phone, Email FROM Contact WHERE AccountId = :con.accountid];
        return null;        
    }
     
           public void DeleteAccount()
           
           {
// if for any reason we are missing the reference
if (SelectedContactId== null) {

return;
}

// find the account record within the collection
Contact tobeDeleted = null;
for(Contact a : Contacts)
if (a.Id == SelectedContactId) {
tobeDeleted = a;
break;
}

//if account record found delete it
if (tobeDeleted != null) {
Delete tobeDeleted;
}
}
}

**VF Page**

<apex:page sidebar="false" controller="DisplayAccWithContact3">
    <apex:form > 
    <style type="text/css">
    .bPageBlock .pbTitle {
     width: 100%;    
     text-align: center; }
     </style>
<apex:pageBlock title= "Account Information"/>
    <apex:outputText value="Enter Account Name:"></apex:outputText>    
        <apex:inputfield value="{!con.accountid}"/>
        <apex:commandButton value="ShowContacts" action="{!showContacts}" rerender="out" status="mystatus"/><br/>
        
        <apex:actionstatus id="mystatus" starttext="please wait contacts are loading.......">
            <apex:facet name="stop">
                <apex:outputpanel id="out">
                    <apex:pageBlock >
                        <apex:pageBlockSection >
                            <apex:pageBlockTable value="{!Contacts}" var="c" rendered="{!con.accountid !=null}">
                            <apex:column >
<apex:outputLink title="" value="/{!c.id}/e?retURL=/apex/{!$CurrentPage.Name}" style="font-weight:bold">Edit</apex:outputLink>&nbsp;|&nbsp;
<a href="javascript&colon;if (window.confirm('Are you sure?')) DeleteAccount('{!c.Id}');" style="font-weight:bold">Del</a>
</apex:column>
                                <apex:column headerValue="Name">
                                    {!c.Name}
                                </apex:column>
                                <apex:column headerValue="Phone">
                                    {!c.Phone}
                                </apex:column>
                                <apex:column headerValue="Email">
                                    {!c.Email}
                                </apex:column>
                            </apex:pageBlockTable>
                        </apex:pageBlockSection>
                    </apex:pageBlock>
                </apex:outputpanel>
            </apex:facet>
        </apex:actionstatus>
        <apex:actionFunction action="{!DeleteContact}" name="DeleteContact" reRender="form" >
<apex:param name="contactid" value="" assignTo="{!SelectedContactId}"/>
</apex:actionFunction>
    </apex:form>
</apex:page>