Is there a simple way to replace an asset id in a group of content without having to manually edit every page? For example I need to replace the string src="./?a=6407" with src="./?a=6704" in about 50 or more pages from a particular root node. The global search and replace doesn't seem to work on html code. Any ideas?
If asset 6407 actually exists, you could just move the content there 
Otherwise, you're right, global search and replace only works on the content that Matrix indexes (ie. not HTML content) AFAIK.
There is probably something you could do at the filesystem/database level, but it wouldn't be worth it for only 50 pages.
Thats what I figured. Just another one of the 2 second tasks in dreamweaver that takes several hours to do in Matrix.
Why are you making the replacement?
If you deleted (say) asset ID 1234 and wanted all the links to then point to 4567, you could set up a redirect to the new location when you deleted it.
If you are comfortable working in SQL, you can make this change In the database:
[sql]SELECT attrid FROM sq_ast_attr WHERE type_code LIKE 'content_type_wysiwyg' AND name LIKE 'html';[/sql]
This gets you the Attribute ID for HTML content in WYSIWYG containers. Let's call this XX.
[sql]UPDATE sq_ast_attr_val SET custom_val = REPLACE(custom_val, '?a=6407', '?a=6704') WHERE attrid = XX AND custom_val LIKE '%?a=6407%';[/sql]
This updates your databse. You now need to update the content cache files. The easiest way to do this is to run the system_integrity_run_tidy.php script that rebuilds WYSIWYG content for you.
Also Raena: Remember that trashing an asset and remapping only fixes external requests to the old URL. It does not replace internal Matrix content, so these links will break if the old asset is deleted. Once it is trashed, Matrix will not be able to expand a real URL for the old ./?a=6407 reference URL.
We imported a bunch of content from our development server, which requires replacing some id's as they don't match up in dev and prod. There was a typo when this was done and we ended up with ?a=6407' instead of '?a=6704'. I figured that replacing the id's directly in the db is the only way it can be done. Thanks for the help anyway.