There appear to be a growing number of law firms which are making some rather colossal mistakes in relation to their websites. (This goes beyond the fact that most legal websites are ugly, poorly designed, and of little value to potential clients.) Among the bigger errors:
Unethical SEO Tricks
Most law firms have no idea what the term "SEO" ("search engine optimization") means - they just hire a designer and say "make my site popular". And their design firm engages in such conduct as cloaking, the use of "hidden div's", and other techniques which are at best frowned upon by search engines. If the firm is lucky, the tricks don't result in a long-term penalty. If the firm is unlucky, their next web designer may have to plead with search engines to forgive a penalty that excludes their site from search results or relegates it to the 100th page.
Not Owning Your URL
Some services which market law firm sites to lawyers maintain ownership of the URL assigned to the site. As a consequence, if the law firm decides to change to a different designer or hosting service, the law firm may have to abandon the URL. Law firms should always be sure that they own their own URL. (A related error: not owning your site content. When you purchase web design services, make sure that should you change designers or hosts you will be able to claim ownership of your existing site.)
Obtaining an Expired URL
It is difficult in this age to find a URL which has not previously been owned by another company. Granted, if you pick a name that is sufficiently unique that might not affect you, but if you are seeking a name that is catchy or memorable it is likely that somebody else has owned the name before you. If you aren't careful, you may find that the prior owner abused the URL, committing violations of search engine submission rules, and that the URL has been downgraded within search results - or even completely excluded from them.
Using Boilerplate Content
One of the biggest keys to producing good traffic through search engines is to present informational content - articles, FAQ's, etc. Some legal web designers offer boilerplate content for websites. Search engines favor unique content, and sites which rely on boilerplate will have a difficult time getting good placement in search engine results pages.
Using Plagiarized Content
Even worse than boilerplate content, some law firms use web designers who "shortcut" the design process by stealing content from other sites. Not only does this implicate the same sort of "duplicate content" penalty as boilerplate material, it can be quite embarrassing for a law firm to be caught presenting plagiarized material as its own. (I am not aware of any litigation against law firms, or any ethics complaints, on the basis of plagiarism - but those possibilities exist as well.) Law firms should ensure that their contracts with their web designers require original content (text and graphics) and should exercise some level of due diligence (e.g., searching for phrases in Google) to try to confirm that the content is not simply lifted from other websites.