|This month, Paul Grosse gives you more insight into
some of the topics dealt with in HelpDesk and HelpDesk
HTML 'Alt' tags
Many websites do not use the html alt tag with images and as a result, people who either cannot download images or have no use for them are offered little useful information when browsing the site thus making navigation almost, if not actually, impossible.
tag has been supported since Netscape 2 and Internet
Explorer 2 and since Netscape 4 and IE 3, moving the
mouse over an image displays the alt text in the same way
that tool-tips are; for example in the screenshot snip on
the right. Alt text is now considered 'required' if your
pages are going to be useable.
The alt text is put into the html page either as alt text in an image properties dialogue box on your WYSIWYG html editor or in the html code itself as follows...
<img src="images/sheep.jpg" alt="flock of sheep" align ="right">
would present itself as the picture on the right. Just
hover the mouse over the image if your browser does this.
You have to be careful with tags though because you can put together images with descriptions that, whilst sounding innocent in their own right, can produce curious effects. For example...
So, if your site is intended to be a useful and useable source of information that is easy to navigate, as opposed to just some pointless graphics, you need to use the alt tags and also be careful so that their content is not ambiguous or consists entirely of "blue bullet, red bullet, red bullet, yellow bullet..."
.png images - graceful degradation
One other thing to remember about images is the format of them. Many people have started to use Portable Network Graphics (.png) files and like .gif s, they carry alpha channel (transparency) information. However, where a pixel in a gif is just on or off, in a png, it can be set to any level therefore drop shadows or other images can be used so that detailed backgrounds can be made use of.
One of the principles of the Internet is that the browsing experience should be made as good as possible and as inclusive as possible. Unfortunately, some people make sure that their site is aimed at only IE6 or whatever so everybody else has to put up with a degraded experience. The same is true with png files - not all browsers are advanced enough to support alpha channel levels between the extremes.
The graphic below is a png file on a blue background and makes use of a drop shadow.
As you can see, under GNU/Linux (Konqueror), it is reproduced properly but under Microsoft Internet Explorer 6 it is not - IE6 is not as advanced at this stage so you should really use png files without transparency if you are to make your site available for people with Microsoft systems that do not yet understand how to use png files properly.
If the image of the png file on the left appears properly, your browser is ready for this new (20th Century) innovation.
The Problem and Existing Solutions
If you need to have your email address on a website, you have a problem with spiders crawling for mail addresses and this then being passed on to spammers as; "buy our list of 10 million genuine email addresses for only $xx"
One solution to this was to put "NOSPAM" into the address so it might read "joeNOSPAMbloggs@foobar.com" with the intention of the user removing it before they sent you the mail thus leaving "email@example.com". However, there are programs that will remove this automatically.
Other tactics include presidents names and so on but you are assuming that the genuine sender has the requisite knowledge.
Interestingly, I receive spam email to addresses that have never existed - they are either guesses (find a mail domain and prefix it with "info@", "sales@" "admin@" and so on) or completely made-up "o8hllln@", "f64gopp98@" and so on. Clearly, even the people selling the millions of email addresses are padding out the thousands they have harvested with others that they have just made up to fill the gaps.
Spam is effectively one of a group of email activities that you can call "unauthorised" and therefore use an authentication system to block unauthorised email. Instead of trying to guess if it is unauthorised, 'know' that it is authorised.
Body Content Filtering Systems
Normal mail filtering systems rely on trying to guess whether or not a message is spam by looking at the type of wording of the mail and whether there are certain clues such has heavily disguised URLs and so on - using escape characters instead of normal typeable characters such as http://. If you look at the source for a lot of spams, the 'forbidden words' are divided up with html tags that are just made up - html that is not understood is just ignored - so when the words are displayed, they appear as though they were meant to by the spammer so, a text containing the 'forbidden word'; "finance" would appear in the email source as...
...and appear on the recipient's mail program reconstructed as...
All the anti-spam engine needs to do is strip out the html tags to see the message. In response to this, the spammers have started doing the following...
so that when the anti-spam engine strips out the html, it is left with
and is passed through. However, when the end user sees
the word is corrected by their brain.
Tackling spam this way is basically just a guessing game with the spammers hitting the email address target every time so, why not look at it from the other side and make it a double bullseye to hit?
Upping the Cost of Spamming
This particular solution relies on the fact that most (if not all) spammers will have obtained your email address by buying it off somebody else and have never visited your website in the first place. Simply by visiting your website, they can authenticate themselves by reading the string but this will up the cost of emailing 10 million people if they have to visit all of their websites first. If they are prepared to put this amount of effort into contacting you, you can at least read through it (or at least the first bit of the email) before you delete it.
Note that this will stop email from people that have not visited your site but the scammers (Nigerian bank scams and so on) might well visit your site first as there is so much more for them to gain.
Subject Line Content Requirement
The solution is to have on your website a string that must be included in the mail - the subject line being the easiest to see - whose inclusion is the key to going somewhere instead of straight to the deleted folder.
If, on your website, you say...
my email address is firstname.lastname@example.org and you must include "JD3Y" in the subject line
... then any mail that does not include this can just be deleted. If everybody did this then spammers would have to visit all "10 million email" addresses' sites to find the string - they would have to know where the sites were to start with :-).
If you are going to implement this, you need to make sure that the known genuine senders that will fall outside the net can get their email through so one logical filtering procedure to set up on your mail client is...
By doing this, you can get your machine to sort out the half dozen or so genuine emails from the 200 spams you get each day.
Images - negatives and colours.
Based on Debian, KNOPPIX is a GNU Linux distribution that runs entirely off a CD ROM. It only needs you to have a computer that will boot off the CD ROM (or a floppy disk and then the CD ROM) and have enough RAM (I have run it on a 200MHz Pentium MMX with 96MB of RAM with no problems). In fact, it doesn't matter whether or not your machine has a hard drive, it will work just as well without it as long as it has at least 82MB of RAM or, if you want to use it in text only mode, 20MB of RAM.
Getting a copy on CDR
First of all, you need to have a copy on CD. On the SuperDVD this month, we have the ISO image for KNOPPIX 3.3 which you should burn to a CDR. Instructions of how to do this are elsewhere on this disc but for those who cannot wait, you just copy the ISO file to a suitably large and fast drive on your computer and then burn it to a CDR. In Nero, get rid of the Wizard and click on File/ Burn Image, select the image from where you stored it, click on 'Write' and let it get on with it.
KNOPPIX will load up and present a desktop environment that is very similar in many ways to Windows. On the desktop, you will see the trash can and any disks and other media that you might have on that machine.
You will note that there are some - or at least one - cryptic looking labels for your hard disks. Instead of drive C:\, D:\, E:\, F:\ and so on, where, say C:\ and D:\ are the same physical drive with two partitions and E:\ and F:\ are another drive with two partitions, you will see something else. Physical drives are given letters and the partitions are given numbers. So, in this case, C:\ will be hda1, D:\ will be hda2, E:\ will be hdb1 and F:\ will be hdb2. If you have a usb drive - whether it is a flash drive or a large external drive - it should be called sda1 (and so on).
Along the bottom is the taskbar and if you click on the 'K' on the far left, you get a menu like the Start menu in Windows.
USB FlashDisk or LAN
For backing up or rather, recovering data, the big question is: "Ethernet or sneakernet?" If you have a LAN that you can plug the computer into, everything is a lot easier to do even if it is just one other machine and a crossover link. If you have not, you will have to use some other form of storage device to act either to hold the lot or as a bucket brigade to ship the data chunk by chunk to another machine.
A bit about the GNU/Linux file system compared to Windows
Windows uses the drives as a root to the directory tree and more recently, has the desktop as the tree root with My Computer and Network Neighbourhood running off that with the drives under My Computer and other network shares under Network Neighbourhood. (This is ignoring all of the other stuff in there like recycle bins and so on). Thus...
GNU/Linux has a similar directory structure with the root directory (not to be confused with 'root') at the base of everything with various directories off that. Within this semi-virtual/ semi-real file structure, various disks are 'mounted' in various positions as are network shares. It is irrelevant what file system each uses as they are considered (broadly) equivalent by the file system. Extra drives (those that are not part of the GNU/Linux system) are usually mounted in a subdirectory called /mnt (the leading slash meaning that the directory path is absolute).
The devices are to be found in a directory called /dev so this is what you will find when you look at the properties box - something like /dev/hda1 which will be mounted at /mnt/hda1. If you were going to look at the contents, you would look at where it was mounted because there, it is translated into the file structure. If you look at it in the /dev directory, you will see the raw data on the disk.
If we created a directory called /lan and mounted the network shares on that (remembering to create the subdirectories first) we could end up with a structure that is very easy to navigate. Thus...
Windows likes to inhabit the entire and only partition on the first hard drive so if it is Windows that will not boot up, it is likely that you will find any data that you need on hda1 as the other drives should be okay (unless you have Windows spread out and it is one of these that has become corrupted).
FlashDisk or USB Drive
If you have a flaskdisk or another USB-based mass storage device, it will probably appear on the desktop as sda1. Before you click on it, you want to make sure that it is mounted into the operating system as writeable rather than read-only.
Right-click on the icon (sda1) and
then, in the Device tab, uncheck the Read Only checkbox.
Click OK and then click on the desktop icon to mount it
and display it in the file browser
Setting up the LAN
If your LAN uses DHCP (Dynamic Host Configuration Protocol), all you have to do is click on the KNOPPIX penguin on the taskbar - the second from the left - and select Network/Internet | Network card configuration and when asked if you want to use DHCP broadcast, click 'yes' - the computer will do the rest.
If your LAN does not use DHCP or you want to specify the settings yourself, click on the KNOPPIX penguin on the taskbar, select Network/Internet | Network card configuration and when asked if you want to use DHCP broadcast, click 'no'. Next, enter the IP address - eth0 is the ethernet card (it might be that you are using something different or that you have two cards (if it is the latter and you don't know which is eth0, set up eth0 and if it does not work, you can go back to this dialogue as many times as you like until it works the way you want it)). Next, enter the network mask - it will guess at this (see previous PC Plus HelpDesks for how) - then the broadcast address, the default gateway and the name servers and then it will set up the card for you.
Just to test it out, load up a copy of Konqueror and point it at a webserver
Pushing or pulling data on the LAN
GNU/Linux was built from the bottom up with networking and compatibility in mind therefore it has a lot of options of how to transfer data. You can either pull it across the network using FTP from another machine or you can use Server Message Block (SAMBA) to push data to a Windows machine. If you have your network neighbourhood configured, you already have SAMBA. Otherwise you need to set up network neighbourhood on Windows.
smb:/ as an alternative
Everyone is familiar with typing http:// at the address bar of Internet Explorer or their favourite browser but in GNU/Linux, there are more options. In issue 214, we mentioned KIOSlaves. Here, we are going to use one. If, on the KNOPPIX machine, we type smb:/, we should be able to navigate our way to the target machine by selecting workgroup, machine, share and so on - eventually leaving us with a window that we can see the contents of - files and directories.
If you encounter the problem of having navigated part of the way to your destination, only to be told that you cannot get there for some reason (not found and so on), try deleting the workgroup name in the address thus:
WARNING: if you are copying the files to a drive on the machine you are running KNOPPIX on, do not copy to a partition that is formatted as NTFS unless you know for sure (have checked yourself) that the version of GNU/Linux you are using will write safely to NTFS. As an aide-mémoire, think of NTFS as Not That File System.
Just drag and drop
If you have two browser windows open, one at your source directory and one at your destination (whether it is an smb connection across your LAN or directly onto an sda or another hda) you can now simply highlight the files you want, drag them from one browser window and drop them into the other.
With your files now safe, you can locate SCANDISK, if you have not already (use the find option in KDE under the Tools menu) and then you are ready to start recovering your Windows functionality.
One word of warning - whilst you are in KNOPPIX, your hard drive is protected so that you cannot damage it (unless you have made it writeable) so you have an unfamiliar, professional operating system that is free to explore. In the games menu, under 'Tetris-like', you will see a game called 'Frozen Bubble'. By all means, have a play with it but when you realise that you can hear the dawn chorus outside, remember that this is highly addictive and you should limit your time spent playing with it (strictly). For those who are morbidly curious, the screenshot on the right is at level 70.
You might toying with the idea that you prefer GNU/Linux over Windows any way and decide to install it instead - with KNOPPIX, you have an opportunity to play around and get a feal for it without damaging your existing installation (such that it is).
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