Every Tumblr theme includes basic components common to all Tumblr blogs, such as access to an RSS feed, the blog's archives and a text field for searching the site. The search text field is created using a form tag, an HTML command that provides the browser instructions for displaying the text field and directions to the blog's database. To remove the search text field on your Tumblr blog, you must access the site's HTML, find the form tag associated with the search text field and erase it from the document.
Go online to Tumblr, type the email address and password associated with your Tumblr blog in the corresponding text fields and press "Enter." Tumblr displays your dashboard.
Click "Customize" under your Tumblr blog's name in the right-side bar.
Click "Themes" in the top menu bar and click "Use Custom HTML" at the bottom of the "Themes" drop-down window. Tumblr displays the HTML that composes your blog.
Press "Ctrl" and "F" simultaneously on your keyboard to activate your browser's "Find" feature, type "". Press "Delete" to erase the highlighted search form HTML.
Click "Save and Close" to apply the changes and return to your dashboard.
Rather than remove the form tag, insert HTML that hides the tag from your browser. Place your cursor just before the form tag and type "<!--". Then, place your cursor after the end of the form tag and type "-->".