A conditional template tag in Blogger looks like following

<b:if cond='condition_expression'>
    <!-- content when condition is satisfied -->
</b:if>

List of Conditional tags for page types

Archive page

<b:if cond='data:blog.pageType == "archive"'>
<!--archive_Page-->
</b:if>

Error Page (404)

<b:if cond='data:blog.pageType == "error_page"'>
<!-- all error pages-->
</b:if>

Index Page

<b:if cond='data:blog.pageType == "index"'>
<!-- all index pages -->
</b:if>

Homepage

<b:if cond='data:blog.url == data:blog.homepageUrl'> 
<!-- only homepage -->
</b:if>

Item (post) pages

<b:if cond='data:blog.pageType == "item"'>
<!-- all item pages -->
</b:if>

Specific Post by URL

<b:if cond='data:blog.url == data:blog.canonicalHomepageUrl + "2014/08/foo.html"'> 
<!-- a item page from august 2014 with post-title 'foo'-->
</b:if>

Label page

<b:if cond='data:blog.searchLabel'>
<!-- all label pages -->
</b:if>

Specific Label Page

<b:if cond='data:blog.searchLabel == "foo"'>
<!-- for label 'foo' -->
</b:if>

Search page

<b:if cond='data:blog.searchQuery'>
<!-- all search pages -->
</b:if>

Specific Search Query page

<b:if cond='data:blog.searchQuery == "foo"'>
<!-- for query 'foo' -->
</b:if>

Static page

<b:if cond='data:blog.pageType == "static_page"'>
<!-- all static pages -->
</b:if>

Specific Static page by URL

<b:if cond='data:blog.url == data:blog.canonicalHomepageUrl + "p/foo.html"'> 
<!-- a specific static page with name 'foo' -->
</b:if>

AND/OR/NOT

AND

<b:if cond='data:blog.pageType == "index"'>
  <b:if cond='data:blog.searchQuery'>
    <!--search_page AND index_page-->
  </b:if>
</b:if>

OR

<b:if cond='data:blog.url == data:blog.canonicalHomepageUrl + "p/foo.html"'> 
  <!-- static_site foo OR static_site bar -->
      <b:else/>
<b:if cond='data:blog.url == data:blog.canonicalHomepageUrl + "p/bar.htm"'> 
  <!-- static_site foo OR static_site bar -->
   </b:if>
</b:if>

NOT

<b:if cond='data:blog.pageType != "item"'>
  <!-- all pages except item pages -->
</b:if>

<b:if cond='data:blog.url != data:blog.homepageUrl'> 
  <!-- all pages but NOT homepage -->
</b:if>

How to Use conditional tags

To apply a conditional tag to some content, simply put the content inside the opening <b:if cond…> and the closing </b:if> like:

<b:if cond='data:blog.pageType == "item"'>
    # THIS CONTENT WILL BE EXECUTED IF CONDITION IS TRUE
</b:if>

In the example above, the content will only appear on post pages.

The content can be a div, a section, a style tag or another conditional tag etc.

If you want to specify a alternate content (when the condition is false), you need to insert a <b:else/> tag followed by the content, like this:

<b:if cond='data:blog.pageType == "item"'>
    # THIS CONTENT WILL BE EXECUTED IF CONDITION IS TRUE
    # i.e. if current page is post (item) page
<b:else/>
    # THIS CONTENT WILL BE EXECUTED IF CONDITION IS FALSE
    # i.e. if not post page
</b:if>

The <b:else/> also works like an OR operator as explained above.

Examples - Remove Sidebar from specific blog Page / Post

Note: When you create post or page, look at your Browser address bar to get postID or pageID of the page or post and replace with the number in the example below.

<b:section cond='data:view.postId != 123456' class='sidebar' id='sidebar_feed' name='Sidebar' showaddelement='yes'>

<b:section cond='data:view.pageId != 123456' class='sidebar' id='sidebar_feed' name='Sidebar' showaddelement='yes'>

<b:section cond='data:view.postId not in [123456,234567,345678]' class='sidebar' id='sidebar_feed' name='Sidebar' showaddelement='yes'>

<b:section cond='data:view.pageId not in [123456,234567,345678]' class='sidebar' id='sidebar_feed' name='Sidebar' showaddelement='yes'>