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COPY&PASTE BELOW CODE  AND SAVE AS HTMLPAGE.html
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<font size="6">Type some HTML here:</font></b></p>
<FORM name="K">
<P style="margin-top: 0; margin-bottom: 0">
<TEXTAREA NAME="ta1" rows="15" cols="50">
</TEXTAREA>
</FORM>
<BUTTON TYPE="button" NAME="test5" ONCLICK="r=window.open();r.document.write(document.forms.K.ta1.value)">
Generate Page
</BUTTON>
<BR>
<BUTTON TYPE="button" NAME="test4" ONCLICK="if (typeof(r.rb)=='undefined') {r.window.close()}">
Close Page
</BUTTON></td>

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ReadMore:
http://www.adobe.com/uk/products/edge-code.html
https://codemirror.net/demo/preview.html
https://www.froala.com/wysiwyg-editor/docs/examples/live-code-preview
http://www.htmlinstant.com/
http://scratchpad.io/dramatic-scale-4047
http://www.ultraedit.com/support/tutorials_power_tips/ultraedit/integrated_html_preview.html
http://www.w3schools.com/html/tryit.asp?filename=tryhtml_basic
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