Free editing in Sourcecode

Hello,

I hope it is the right forum for asking my question.

I tried to edit a html element in sourcecode by adding some (correct) styles. But somehow the inserted source code was cleared.

Is it possible to deactivate this feature so I can edit some random text in the future?
For example:

<div style="background-color:#FF0000;color:#FFFFFF">example</div>

or:

<fakeelement style="display:none">...</fakeelement>

Thanks