Remove .button styling from _default_wp_die_handler()

[ryan]

These styles seem to be a left over from the install styles. Given that wp_guess_url() is not a reliable way to determine the siteurl from a front page load and that core doesn't seem to need these styles for any of its wp_die() messages, let's remove them.

Plugins might be more likely to include Go Back type buttons, so maybe we should preserve some styling. The image gradients need to go though because wp_guess_url() doesn't really work here.

Related: [19417]

Use css3 gradients instead of images and call it good enough?

To test:

• Remove wp-config.php
• Visit wp-admin/install.php
• Note the "Create a Configuration File"
• Make the button pretty without using images and wp_guess_url()

Replace the button(s) background images with a gradient

In [19635]:

Replace background image with CSS3 gradient in wp_die(), fixes #19701

In [19636]:

Replace background image with CSS3 gradient in wp_die(), fixes #19701 for 3.3

Replying to ryan:

Use css3 gradients instead of images and call it good enough?

Yes, my intention was for us to revisit all our button styles and change to CSS3 so this sounds like a perfect first step.