does anyone know what that tag means?? how it works??

thankz in advance!

That is microsoft office tags. You get it when you copy from office programs like word or outlook emails directly into your web editor, without removing the microsoft formatted tags.

Never copy from word or email and paste stuff directly into web. First, remove the format as follow:

Copy the text you want to use and paste it in Notepad. Then copy the clean, unformatted text from notepad into your website. Notepad is a text only editor, and it will strip any formatted text clean.

thank you! one more question if you don't mind?

<![if !vml]>...<![endif]-->

is that the same?

vml is Vector Markup Language that may also be there because of text copied from other formats without removing the format before pasting in your web editor.It is a deprecated XML language.