How can I enclose the content section of my blog to display any items(JPEGs/video) to a certain width??? I'd like to re-size only if the items are larger then "...px"

I currently use 'blogger', I can either manipulate the html for my entire blog or make up tags to use when needed inside individual posts...I've been attempting things with the div tag unsuccessfully for hours so I though it best to ask after so many failed attempts.

Thanks regardless

I'm new on this but I think you can do it using CSS

In your template (HTML View) search for </style> inside <header> and put some like this above.

In CSS

.content {
    [your content css]
}

.max900 {
    max-width:900px
}

You can customize the "...px" above.

In HTML

Then in your blog content, in HTML View, define classes "content" and "max900":

Lorem ipsum dolor sit amet, consectetur adipiscing elit.

  <div class="content max900">
      Maecenas ut tellus lorem, in mattis ante.
      <img class="max900" src="image.jpg" />
  </div>

Nulla aliquam, sed venenatis erat lorem sit amet dolor.

PS. Sorry for my English.