I believe this is similar to what you are trying to achieve without the javascript

<apex:page showHeader="false" standardcontroller="Blog_Post__c" extensions="blogExtension">

<apex:stylesheet value="{!$Resource.blogStyle}"/>   <!-- extracted from blogger.css -->
    <link rel="stylesheet" type="text/css"
        href="http://www.blogger.com/css/blogger.css" />

<div id="body">
<div id="main-wrap">
<div id="main" style="margin-top: 5px">
<div id="m2">
<div id="m3">
       <apex:image id="banner" value="{!$Resource.GatesheadSmall}"/>
<br />     
<h2 class="title"><apex:outputtext value="{!thispost.name}" /></h2>
<br />
<br />
<apex:outputText value="{!thispost.Post__c}" />
<apex:outputPanel id="main">
<br />
<br />
<h3>Comments</h3>
<br />
<br />

<apex:repeat value="{!thispost.Comments__r}" var="comment"
            id="comments"><h4>{!comment.name}</h4><br />
{!comment.Body__c}<p/>
            <hr />
        </apex:repeat>
</apex:outputPanel>

<apex:form >
Title: <BR />
<apex:inputField value="{!newComment.Name}"/> <BR /><BR />
Email:<BR />
<apex:inputField value="{!newComment.Email_Address__c}"/> <BR /><BR />
Body: <BR />
<apex:inputTextarea cols="100" rows="5" value="{!newComment.Body__c}"/>
<BR /><BR />
<apex:pageBlock >
<apex:pageBlockButtons location="bottom" >

<apex:commandButton styleclass="groovybutton" value="Save"  action="{!saveNewComment}"/>
<apex:commandButton styleclass="groovybutton" value="Go Back" action="{!blog}"/>
</apex:pageBlockButtons>

</apex:pageBlock>
 </apex:form>
</div>
</div>
</div>
</div>
</div>

</apex:page>

public class blogExtension {
    public PageReference menu() {
           PageReference pageRef= new PageReference('/apex/GCMenu');
                pageRef.setredirect(true);
                return pageRef;
    }



        public PageReference edit() {
                Id id = System.currentPageReference().getParameters().get('id');
                PageReference pageRef= new PageReference('/apex/blogDetail' + '?id=' +
                id);
                pageRef.setredirect(true);
                return pageRef;
        }
        
        
        
        public class post {
                public Blog_Post__c bpost {get; private set; }
                public Integer numberofcomments { get; private set;}
                public post( Blog_Post__c b) {
                        bpost = b;
                        numberofcomments = bpost.Comments__r.size();
                }
        } 
        public list<Blog_Post__c> blogList { get; private set; } 
        public blogExtension() { 
               
                blogList = [Select b.Post__c, b.Name, b.Id, createdby.name,createddate,
                        (Select Id, Name, 
                        Email_Address__c, Body__c, Blog_Post__c From Comments__r) 
                        From Blog_Post__c b];   
        }
        public list<post> getPosts() {
                list<post> ret = new list<post>();
                for ( Blog_Post__c bl : blogList) {     ret.add( new post( bl) ); }
                return ret;
        }
        

        
        public PageReference newBlog() {
                PageReference pageRef= new PageReference('/apex/blogedit');
                pageRef.setredirect(true);
                return pageRef;
        }

       public PageReference blog() {
                PageReference pageRef= new PageReference('/apex/blog');
                pageRef.setredirect(true);
                return pageRef;
        }

/* for use as an extension, blogDetail.page 
 */
        /*was final*/ ApexPages.standardController controller; 
        ID id { get { return this.controller.getRecord().id; }} 
        
        public  blogExtension(ApexPages.standardController c) {
            this.controller = c;
            init(); 
        } 
        
        public PageReference saveNewComment() {
            insert newComment; 
            return init(); 
        }
            
        public Blog_Post__c thisPost { get ; set; } 
        public Comment__c newComment { get; set; }
        public PageReference init() {
            this.thisPost = [ Select b.Post__c, b.Name, b.Id, createdby.name, createddate, 
                    (Select Id, Name, Email_Address__c, Body__c, Blog_Post__c,createddate From Comments__r order by createddate) 
                From Blog_Post__c b where b.id = :id limit 1];
            this.newComment = new Comment__c( Blog_post__c = id );
            return null;
        }
        
        static testmethod void testFoo() {
        Blog_post__c bp= new Blog_post__c();
insert bp;
        post p = new post(bp);
        Integer g = p.numberofcomments;
        
         blogExtension b = new BlogExtension();
         b.getPosts();
         b.newBlog();
         b.edit();
         b.newcomment = new Comment__c();
         b.newcomment.blog_post__c = bp.id;
         
         ApexPages.StandardController sc=new ApexPages.StandardController(bp);
         
         b.controller = sc;
        
        // b.id = bp.id;
         b.saveNewComment();
         //b.init();
         //List<Blog_Post__c> p = b.blogList();
         //List<post> q = b.getPosts();
         
        }
        
 
}