Tumblr dubs itself "the easiest way to blog." To fulfil this slogan, Tumblr simplifies the process of formatting blog posts. The Add a Text Post page -- the place where you create blog entries -- contains a rich text editor that makes bolding words and adding lines through text a matter of clicking a button. For more advanced users, Tumblr provides an HTML editor.
Sign in to Tumblr and visit your Dashboard.
Click "Text" to begin a new text post.
Type your post in the Post box.
Highlight the text you're formatting.
Click "Bold" to make the highlighted text bold. Click "Strikethrough" to cross out the text. Both options are in the toolbar in the top of the Post box.
You can cross out and bold text on Tumblr by clicking the "HTML" link in the Post box. When the HTML Source Editor opens, type "<strong>" in front of your text to make it bold. To stop bolding text, type "</strong>." To cross out text, type "<strike>" in front of it and "</strike>" after it. Do not use the quotation marks.