The output filters are applied to rendered HTML code. They make various changes to the HTML code before it is sent to the browser:
Form filter
The form filter fixes the issue with non-working postbacks on pages that use URL rewriting. It ensures that forms, dialogs and buttons will work correctly on Kentico CMS-managed pages.
You can exclude pages from this filter by adding their alias path to the Site Manager -> Settings -> Output filter -> Excluded Output Form Filter URLs field, separated by a semicolon (;).
XHTML filter
The XHTML filter fixes some XHTML incompatibilities. It closes unclosed tags, invalid <script> tags, etc.
You can exclude pages from this filter by adding their alias path to the Site Manager -> Settings -> Output filter -> Excluded XHTML Filter URLs field, separated by a semicolon (;).
XHTML errors may also be fixed in the WYSIWYG editor when they are saved. This can also be configured globally through the CMSWYSIWYGFixXHTML web.config parameter (supported values are "true" and "false").
Resolve filter
The resolve filter changes relative URLs in format ~/mypage1/mypage2.aspx to /application/mypage1/mypage2.aspx (application running in a sub-folder) or /mypage1/mypage2.aspx (application running in the root). It changes only URLs inside src and href attributes.
You can exclude pages from this filter by adding their alias path to the Site Manager -> Settings -> Output filter -> Excluded Resolve Filter URLs value, separated by a semicolon (;).
Page url: http://devnet.kentico.com/docs/5_5r2/devguide/index.html?output_filters.htm