I want to make a logo using html css. Can we increase the angle of italic text using css or javascript?
That's not possible with CSS. You could try to switch to another font on i's and em's that has more slanted letters but I don't think that'll help you.
And if you're designing a logo, why are you doing it with CSS? That's what you have Photoshop and/or Illustrator for.
The angle depends on the font you are using. The font designer has to draw the italic version manually. You can't change that automatically.
You can use a skew transform in Firefox, Safari and Chrome. Nothing else is going to support it, and you shouldn't screw around with a font designer's work for a logo design unless you know more about typography than they did anyway. Nobody designs logos in HTML and nobody wants to look at logos in email.
HTML/CSS is the wrong tool for this. Use Illustrator or that kind of software. Or look for a designer.
Make your own font or modify an open source font using a free font-editing tool such as FontForge.
Edit: I see that this is for e-mail with images disabled. Sorry, but it's not possible at all in this case, as most e-mail clients other than new versions of Thunderbird don't support @font-face CSS rules.