Please note: The “Passthrough HTML” feature is still available in Doc-To-Help, but it is recommended that you make use of the Rich Text Variables feature instead. With this feature, you can define a variable in an HTML document and insert it into a Word document.
The Doc-To-Help HTML passthrough feature allows you to include HTML code directly in your document without Word treating the code as text.
Note: HTML Passthrough code is an advanced feature used in Word documents only. HTML Passthrough code should only be used on the rare occasion when it is necessary to insert HTML code into a Word document and an HTML source document cannot be used for this purpose.
To set HTML code as passthrough:
1. In Microsoft Word, select the HTML code to be marked as if you were going to copy it to the Clipboard.
2. On the D2HML
Styles toolbar, click the Conditional Text
button 
.
3. From the Condition dialog box, select the HTML based platform of your choice and check the HTML passthrough code checkbox.
Note: Doc-To-Help does not validate HTML passthrough code, so you should ensure that it works properly before incorporating it into your project.
A note to users of previous versions of Doc-To-Help:
It is no longer necessary to define your code with the HTML character style; any style may be used for your HTML code.
More:
Inserting Files with HTML Passthrough
Code