For perfectly aligned close button, use HTML code (&times) instead of letter x

If you are not happy with the close button (x) of your popup modal dialog box, then try using the HTML code for perfectly aligned cross close button


X             ------  x
&times    ------ ×    (Perfect cross)


Usage Example:

<a aria-label="Close Modal Box" href="#">×</a>


OR


<button aria-label="Close Modal Box">×</button>

For accessibility, use aria-label attribute, otherwise it will read as multiplication when the website used by visually impaired user.