Using Cutting Edge Technology for No Good Reason

It can be very tempting to use the newest technology. But if you put something on your website that is not widely supported by the browsers that visit your site you could risk losing customers rather than gaining them. When you use advanced technology (such as new versions of CSS or HTML), you should use it sparingly and only for elements that are not critical to the page as a whole.

sparingly
控えめに、慎重に

use special effects sparingly
特殊効果を控えめに使う

Water the seeds sparingly until the first sprout appears.
芽が出るまで、種に控えめに水をやります。

Websites That Don't Work in Any Browser Other Than Internet Explorer

Creating a website that only works in Internet Explorer is a very bad business decision. More and more people are switching to other Web browsers like Chrome and Firefox. And if you insist on creating pages that only work in IE, you're deliberately limiting your market share.

deliberately
わざと、故意に、意図的に

He deliberately ignored the error.
彼は、その間違いをわざと無視しました。

I deliberately planned some of my child-rearing techniques.
自分の子育てについて、いくつかの方法を慎重に計画しました。