I often need to make a close button X for different popups, tooltips etc. The easiest solution is to use
× special character that will make a perfect cross ×.
If you don’t use Font Awesome or some glyph icons it’s a perfect and simple solution. You may like to have a cross with a very thin lines, but your cross will look too bold, especially if your main font is bold or the cross is large enough. I’ve found a solution for such a problem.
As a character it could be fine tuned with font-family in CSS. So if no web fonts are used, just add into your CSS file:
font-family:Garamond,'Apple Garamond','Lucida Sans Unicode';
Garamond font will make cross lines light enough. Check this cross, treated with Garamond font: ×