text replacement & seo

I've been having a chat with a designer friend about text replacement and seo. I suspect I've got the wrong end of the stick, but I was under the impression that hiding content from users was bad practice. I'm aware that text is king and of separation of content & presentation. But to me this is a bit of a grey area. Is one considered best practice (with an seo slant)? I don't see one being more semantic than another, I suspect I will stand corrected.

<a href="#" class="delete">Delete</a>

with

background: image(pic.jpg);
开发者_StackOverflow中文版text-indent: -9999px;

or

<a href="#">
   <img src="/delete.png" alt="delete" title="delete"/>
</a>

Good SEO tips:

• provide content valuable for users
• always be honest

If you make src, alt and title the same, they do not add value at all.

I have always used position relative and negative result with good results. For icon buttons there is no difference. Do users consider image icons are more valuable than text links?

Also you should avoid href="#", this is more important in this case than the rest.

BTW, If you make delete buttons crawlable by search engines, they will delete the content ;)