need CSS help

Hi guys,

I am working on a blog page and not able to solve some css problems:

- #blog_text ID not accepting float:left; and height:auto;
- (blog_post_content h1) code not working and H1 applying its parent div's h1 style i.e. blog_text h1

Hope I can get them solved here from you guys.

Thanks

#blog_header {
height:294px;
background: url(../images/blog_header.jpg) no-repeat center top;
}
#blog_content {
margin: 0 auto;
width:940px;
height:auto;
}
#blog_text {
height:1000px; // not accepting height:auto; and float:left; here;
width:940px;
}
#blog_text h1 {
font-family:"Myriad Pro";
font-size:18px;
font-style:normal;
font-weight:bold;
color:#765c4f;
}
#blog_text .hr {
border-bottom: 1px solid #765c4f;
}
#blog_text p {
font-family:Arial, Helvetica, sans-serif;
font-size:13px;
font-weight:normal;
font-style:normal;
color: #765c4f;
line-height:18px;
margin-bottom:12px;
}
#blog_posts {
float:left;
width:620px;
height:auto;
padding-right:20px;
}
.blog_post {
float:left;
width:620px;
height:auto;
padding: 10px 0 10px 0;
border-bottom: solid 1px #ddd7d3;
}
.blog_post h1 {
width:620px;
height:auto;
font-family:"Myriad Pro";
font-size:22px;
font-weight:bold;
font-style:normal;
color: #4f4642;
padding-bottom:3px;
}
.blog_post h1 a {
width:620px;
height:auto;
font-family:"Myriad Pro";
font-size:22px;
font-weight:bold;
font-style:normal;
color: #4f4642;
text-decoration:none;

}
.postdetails {
width:600px;
margin-bottom:10px;
}
.blog_post .author {
color:#a9a19d;
font-family:"Myriad Pro";
font-size:14px;
font-weight:bold;
text-decoration:none;
}
.blog_post .date {
color:#696969;
font-family:"Myriad Pro";
font-size:14px;
text-decoration:none; }
.post .comments {
color:#696969;
font-family:"Myriad Pro";
font-size:14px;
font-weight:bold;
text-decoration:none;
}
.blog_post_content {
width:620px;
margin-top:10px;
font: 400 13px Arial, Helvetica, sans-serif;
}
.blog_post_content p {
width:620px;
font: 400 13px Arial, Helvetica, sans-serif;
}
.blog_post_content h1 {
color:#FF0000;
font-family:Arial, Helvetica, sans-serif;
font-size:20px;
font-weight:bold;
text-decoration:none;
margin-bottom:3px;
}
.blog_post_content h1 a {
color:#FF0000;
font-family:Arial, Helvetica, sans-serif;
font-size:20px;
font-weight:bold;
text-decoration:none;
margin-bottom:3px;
}
.blog_post_content h1 a:hover {
text-decoration:underline;
}

.blog_post_content a {
color:#6d5346;
text-decoration:none;
font-family:Arial, Helvetica, sans-serif;
}
.blog_post_content a:hover {
text-decoration:underline;
}
.post_content img {
margin-top:25px;
}
#blog_sidebar {
float:left;
width:300px;
height:auto;

}