IE6 display issues: login block alignment and checkboxes in moodle forms

I installed moodle 1.8 in my computer and found out some display problems when I use IE 6 to browse the moodle pages.

In the home page, the allignment of the textboxes and the "Login" buttons are not correct. And the checkboxes in the edit profile page are also not displayed correctly.

And there might be some other pages have the display problems withe the textboxes and the checkboxes.

When I use IE 7 or Firefox 2, there is no problem with the display. I think this might be the browser support issue.