Flayra

MySQL uses the index that best matches the query. If you are searching on 2 columns, an index that covers those 2 columns will be used first. Next is an index for either of the columns - if there is an index on both, MySQL will use the index that returns the least results. So as said, if you search on both columns 99% of the time, you really only need the one index that has both columns.

KEY is used to index tables. Usually you index tables for 2-3 columns you often search for (ie: firstname, lastname and e-mail) at the same time. Otherwise it is simply a method to speed up table searching (SELECT queries) but more keys will slow down action queries (INSERT, DELETE, UPDATE queries) since every query needs to manipulate the index files as well. As a consequence, more indexes will also add to the size of the database.

Whitelisting is usually a lot safer than blacklisting. Start with a few files (jpg, gif, avi, whatever you desire) and expand as you test them. With blacklisting someone might manage to get a perl file or some other script file up and execute it. Never put plain-text passwords anywhere. One-way hash them (sha1 - sha256) and compare upon login. Never put the password, in any form, in a cookie or otherwise user-trusted environment. If you need to remember the user, store his ID along with a randomly generated string that is in the DB and should be (almost) impossible to guess. Refresh this string on every login. As for aestetics, please change those colors